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nzjetboating.com Forums => Projects => Topic started by: Jeff B on March 06, 2020, 11:13:45 AM

Title: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:13:45 AM
To do my bit for recycling I decided to recycle this old Yamaha 2 stroke outboard that nobody wanted.
Was pretty heavy but once leg/prop removed the actual engine is under 80kg.
First job is make new intake manifold.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:17:35 AM
Only 2x seized bolts removing leg, pretty good. Biffed that in scrap pile.
Briefly looked at doing bevel gearbox but then I would just have a sportjet nd they stick up a mile high and the gearbox robs power.
Nup, this is going conventional.
Exhaust copied outboard sort of but with performance enhancements..
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:19:04 AM
Carbs stacked in a row, made linkages up to adjust. Works well.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:21:21 AM
Spline in crankshaft is same as jetski driveshaft (pretty handy aye!) 22mm so a polaris driveshaft flipped 180 deg plugs into engine and Kawasaki impeller (20mm spline)
Like it was meant to be.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:24:11 AM
Bit of a guessing game with pump but it's getting a 158mm 2 stage with angry 21 deg front, angry 4 blade 24 deg rear.
We call this the "hyper pump" to tame the mighty 2 stroke torque.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 11:53:40 AM
Makes for a very light, compact setup.
Engine with everything on it running is 96kg
Pump is 26kg + grill (3kg) and bucket (3kg)
Short, 800mm transom to front of engine and low, 500mm total height as there are no camshafts or valves up top.
Similar dimensions as my tipped over L15 honda but with 100hp more.
And I'm guessing about 3x the fuel usage....
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on March 06, 2020, 12:09:51 PM
Awesome Jeff. I harboured dreams of doing similar but with the V8 300hp OMC but they are really hard to get now.
How do you deal with alignment/flex in the driveline? I didnt pick a coupling in there?
How many HP?
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 12:29:12 PM
The splines on driveshaft are ever so slightly curved, this allows for a bit if movement. Alignment still needs to be spot on or the splines will chew out.
Polaris and Seado jetskis are set up like this factory. It's a floating driveshaft

I know of a OMC v8 just down the road getting the same treatment... pop
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on March 06, 2020, 12:32:38 PM
Sweet yep did wonder that, a few things are set up similar. Nice and easy.
Cool! Hopefully they are on the forum and share the love. 2stroke,V8,lightweight. Whats not to like? Fuel use....
Title: Re: 2 stroke comeback.
Post by: steelo on March 06, 2020, 20:40:42 PM
Do you do factory tours?
Title: Re: 2 stroke comeback.
Post by: lachlan on March 06, 2020, 20:42:11 PM
Approved
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 06, 2020, 21:03:40 PM
No tours here, too many health and safety hazards.
Plus I keep all my top secret projects in the back of the shed.
Had a Southern jet trim nozzle that I modified the cone entry on and made new insert, will start at 80.5 and go bigger from there.
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on March 07, 2020, 00:21:45 AM
If Jeff was a Vet He'd make Pigs Fly pig backwards...... Once again you fabricate Amazing dreams in a Health n Safety free zone.......
                                  D_D D_D D_D D_D D_D


                                         :n)
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 11, 2020, 08:42:32 AM
https://youtu.be/zkRhbpJitEI

She is a runner.
Now to build a hull to match...
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on March 11, 2020, 10:19:20 AM
Mean. Its going to be one of the best sounding 2 strokes on the water.
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on March 11, 2020, 10:38:44 AM
Gonna be a screamer- might need some muffling to be useable- I get in trouble with neighbors when I flush my 250 merc  *-)
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 11, 2020, 12:58:03 PM
I'll put a pair of my little 2" transom dumpy mufflers on it.  Will still need to adjust the amount of water injected into chamber to find the "sweet spot" power wise.
It's a 90 deg v6 so has a unique sound. I like it.
Way better than the old 3.8 commy or the VQ35
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on March 11, 2020, 13:23:27 PM
How many hp was the base motor and what size hull you thinking of putting it in? Should go real well.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 11, 2020, 14:04:46 PM
How many hp was the base motor and what size hull you thinking of putting it in? Should go real well.

Base engine is rated 225hp @6000rpm.
I'll put it in a special new
JJ3.0 hull specially designed for 2 stroke, 2 stage propulsion.
Should be under 350kg and tough as (and grunty)  pop
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on March 11, 2020, 14:15:38 PM
Love how you keep innovating Jeff- bloody brilliant. I can't see any issue with this build except the fuel bill potentially it might be horrible

Does anyone know the actual percentage of time spent at WOT in a jet boat?- all of the outboards publish a fuel burn at WOT (its often a scary number) Be curious to see if two strokes actually cost more to run in the bigger engine size- they have better throttle response, are lighter- have lots of power on tap early on?

I am curious... 350kg with 220-ish hp its going to go quite well methinks :-)
Title: Re: 2 stroke comeback.
Post by: steelo on March 11, 2020, 15:10:15 PM
https://youtu.be/zkRhbpJitEI

She is a runner.
Now to build a hull to match...
What about that boat shaped bin under the table?
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on March 11, 2020, 16:32:43 PM
Quote
specially designed for 2 stroke 

What does that involve? Smoke resistant alloy
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 11, 2020, 18:42:38 PM
I'm expecting the fuel consumption to be absolutely terrible....
Not sure on fuel burn but in past experience a 2 stroke uses about 30% more fuel no matter how you drive it.
In reality it comes down to weight you are pushing and how fast you are pushing it?
I'm expecting a good ratio of "fun per litre of fuel" on this one. ;)
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 11, 2020, 18:44:14 PM
What does that involve? Smoke resistant alloy

Special design which optimizes the power characteristics of the engine/pump combo.  :P
Title: Re: 2 stroke comeback.
Post by: Paul on March 11, 2020, 20:36:01 PM
I'm expecting the fuel consumption to be absolutely terrible....

The cost of 2-smoke oil will be the real killer..
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 12, 2020, 15:17:43 PM
Speaking of fuel and oil running costs that will surely send me broke I made fuel tank. Hold enough that my ears will be ringing and I'll be sick of it before I run low on fuel.
Title: Re: 2 stroke comeback.
Post by: Jeff B on March 12, 2020, 15:19:58 PM
Bench seat was going to be a bit dodgy at 60mph so put buckets on heavy duty adjustable rails so can move driver seat 200mm closer to centre when solo.
And can move seats to suit driver/passenger weight.
Title: Re: 2 stroke comeback.
Post by: Clint640 on March 13, 2020, 10:50:21 AM
Nice work! Ya need a disengage setting on the seat sliders & a good solid Jesus bar then the passenger can shift their weight on the go for better cornering like a racing sidecar swinger  )1

Cheers
Clint
Title: Re: 2 stroke comeback.
Post by: lq4151 on May 10, 2020, 19:08:09 PM
I have offten wondered what an engine like that would go like laided down and  coupled  To a jet . Well done Jeff
Your projects are a  inspiration to all keep it up. I'll keep a keen eye on this project 
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 10, 2020, 19:10:50 PM
Not much happening lately, engine and pump all set up, ready to go.
It is a very compact setup.
I'll get back into it soon
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 10, 2020, 19:12:35 PM
.
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 10, 2020, 19:15:00 PM
The jet unit has been named.
Definitely an up market version of mohawks "super pump"  ;)
Title: Re: 2 stroke comeback.
Post by: lq4151 on May 10, 2020, 19:21:54 PM
Great looking set up my guess is it will go very well.
Should sound great at .
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on May 10, 2020, 20:05:00 PM
Forgot about this project! Looking mean. Valvoline 2 stroke eggbeater oil has always treated me well. Good price at Supercheap when on special.
Title: Re: 2 stroke comeback.
Post by: Allen M on May 12, 2020, 08:23:25 AM
The jet unit has been named.
Definitely an up market version of mohawks "super pump"  ;)
We need more details on what?s inside it pop
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 12, 2020, 09:47:54 AM
We need more details on what?s inside it pop

There are some pics further back but I'm using a Skat trak Kawasaki front impeller progressive 16-21.
Rear is JJ custom 4 blader 24 deg duplex 2205 parallel hub beast.
Hopefully turns stones into smoke....
I have shoved 5x ball bearings in pump.
Stator/bearing assembly and the 2x wear rings are all one piece machined as a whole so impeller alignment is perfect and can get tight tolerances. (Not that they will be for long)  ::)
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on May 12, 2020, 14:09:35 PM
Whats the seal arrangement for keep water out of the bearings?
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 12, 2020, 17:11:21 PM
Whats the seal arrangement for keep water out of the bearings?

Lip seals and wear sleeves, 2 in front and 3 in back.
Front of rear impeller is counter bored so close to bearings.
Similar to jetski pump setup.
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on May 12, 2020, 17:35:33 PM
Quality set-up.
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 15, 2020, 20:11:11 PM
Bottom.
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on May 15, 2020, 22:41:47 PM
That thing is going to go like crap off a shovel. Bit low in the sides though. C""
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on May 15, 2020, 22:43:32 PM
The fun police got me. I had written s#$t off a shovel. Jacinda is moderating swearing now too.
Title: Re: 2 stroke comeback.
Post by: Paul on May 15, 2020, 23:30:05 PM
The fun police got me. I had written s#$t off a shovel. Jacinda is moderating swearing now too.

It's the forum software - not Aunty.  It's been in place for many years, there's only a few triggers.
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on May 16, 2020, 08:51:21 AM
It'll Smoke like TuTae of a Kumara Ko...... Better call it Judith too! Cause that pump will crush rocks like Collins wanted minced boy racer cars..... Will Spit them out like Shotcrete....... B))T B))T B))T

Title: Re: 2 stroke comeback.
Post by: Jeff B on June 07, 2020, 19:53:43 PM
Engine all mounted.
Title: Re: 2 stroke comeback.
Post by: glocko on June 08, 2020, 18:35:27 PM
been looking for some new seats ,where did you find these ones ,look good.what sort of weight are they,cheers glocko
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 08, 2020, 18:53:16 PM
been looking for some new seats ,where did you find these ones ,look good.what sort of weight are they,cheers glocko

I get them from Burnsco, I like them with the flip up front.
Title: Re: 2 stroke comeback.
Post by: glocko on June 08, 2020, 18:57:44 PM
sweet, b> b>cheers
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 08, 2020, 20:25:00 PM
I think they are about 7.5kg each?  I cant be bothered unbolting them from.my fuel tank haha.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 10, 2020, 09:28:18 AM
The super duty 2 stroke hull taking shape.
10mm delta, + 12mm plastic.
Std 2 piece transom, 5, 2
5
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 10, 2020, 19:49:14 PM
Hull mostly done now.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 19, 2020, 20:49:12 PM
The business end.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 19, 2020, 20:51:45 PM
Plonk the engine in.
Looks pretty small in there....I feel like it needs a turbo or something to make it more manly? Looks too small with no camshatlfs or other big heavy gear on top of engine...
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 19, 2020, 21:01:43 PM
Looks gorgeous to me. Can't wait to see it screaming down the mighty waikato
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 20, 2020, 12:29:35 PM
Looks gorgeous to me. Can't wait to see it screaming down the mighty waikato

Screaming UP the waikato you mean....
Always head upstream on first couple runs..... ::)
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 20, 2020, 17:55:37 PM
I got faith man, I got lots of faith  O0
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 20, 2020, 20:27:57 PM
Exhaust done.
Twin pipes.
Title: Re: 2 stroke comeback.
Post by: Allen M on June 21, 2020, 09:31:31 AM
Plonk the engine in.
Looks pretty small in there....I feel like it needs a turbo or something to make it more manly? Looks too small with no camshatlfs or other big heavy gear on top of engine...
Wait till you see how much gas this baby sucks   >>@
The size of your fuel tank may well  make up for the lack of engine size.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 21, 2020, 15:38:15 PM
Wait till you see how much gas this baby sucks   >>@
The size of your fuel tank may well  make up for the lack of engine size.

I'm thinking that WOT will be sucking close to 100 litres/hour?
Cruise 25 litres/hour?
Its 2.6 litre and most of the fuel/oil will blow straight out the exhaust, some will get turned into noise and heat...
What's left will turn the jet unit and hopefully make enough thrust to have some fun. B))T
Title: Re: 2 stroke comeback.
Post by: Paul on June 21, 2020, 16:36:18 PM
What's the compression ratio on these things? Can you get revised bits to alter CR, pistons, or reed valves, etc?
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 21, 2020, 17:04:30 PM
What's the compression ratio on these things? Can you get revised bits to alter CR, pistons, or reed valves, etc?

I'm not entirely sure of the compression ratios but it's on the high side on this particular engine (225hp) it's the gruntier model of this engine size family, 150, 175, 200, 225 all have same 2.6 litre capacity.  I will check compression after I fry the first piston.
This actually has a fancy ecu and knock sensor so pulls timing back if I put crappy octane petrol.in it and it pings. b>
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on June 22, 2020, 08:50:50 AM
Looking good. Its going to be a fun boat!
Who do you use to source the silicon exhaust bends? WAM brand?
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 22, 2020, 08:59:17 AM
Looking good. Its going to be a fun boat!
Who do you use to source the silicon exhaust bends? WAM brand?

It's a local shop.
"Hose shop" or something? Used to be called United flexible, they have shops in a few towns in NZ. Do hydraulic hose and all sorts.
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on June 22, 2020, 10:12:27 AM
Is it called Pipeline?
Title: Re: 2 stroke comeback.
Post by: mohawk on June 22, 2020, 12:13:26 PM
Is it called Pipeline?
yup
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 22, 2020, 14:26:35 PM
I'm thinking that WOT will be sucking close to 100 litres/hour?
Cruise 25 litres/hour?
Its 2.6 litre and most of the fuel/oil will blow straight out the exhaust, some will get turned into noise and heat...
What's left will turn the jet unit and hopefully make enough thrust to have some fun. B))T

My 250 EFI Mercury (litre block) burns 156 litres per hour WOT- they love the dino juice no doubt.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 23, 2020, 07:26:59 AM
Reverse fitted. Keeping it light and strong. Locks over centre so no chance of bucket falling down.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 23, 2020, 07:29:16 AM
Making engine cover. 2.5mm, couple folds to match foredeck and stiffen it up a bit. Light and strong...
Gotta keep an eye on weight to keep to my goal of 1.5kg/hp ratio.
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on June 23, 2020, 07:50:07 AM
I like it, very nice proportions for a wee boat.
Smooth
Silky
Sleek
Nothing like the engine......

Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on June 23, 2020, 08:31:42 AM
It's a local shop.
"Hose shop" or something? Used to be called United flexible, they have shops in a few towns in NZ. Do hydraulic hose and all sorts.

http://hoseshop.co.nz/our-products

Select from products in the left hand margin
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 23, 2020, 08:33:16 AM
I like to think of this build as comparable to the "CR500" of jet boats.  l-l
Title: Re: 2 stroke comeback.
Post by: quattro on June 23, 2020, 09:43:49 AM
Will you be doing any port work on it? I don't know how much power people get out of those engines but a guy I know in the states has a 3.3l omc v6 making 400hp. Would give a very good pwer to weight ratio
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 23, 2020, 10:03:13 AM
Will you be doing any port work on it? I don't know how much power people get out of those engines but a guy I know in the states has a 3.3l omc v6 making 400hp. Would give a very good pwer to weight ratio

I'm not planning on porting it. Partly because I don't really know what I'm doing and partly because it will likely turn something that is terribly inefficient into something that is truly horribly inefficient...
I have some valuable knowledge from guys that have raced these engines as outboards but I'm still not sure how my pump will match the power curve yet.  pop
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 23, 2020, 20:20:57 PM
Hull finished welded up.
Hook up some hoses, cables and wires and it will be ready to rumble.
Title: Re: 2 stroke comeback.
Post by: Markg on June 23, 2020, 20:51:10 PM
 pop pop A lot of people watching this one.Almost as fuel efficient as the turbine build.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 24, 2020, 21:31:04 PM
Fuel tank fitted, 44mm filler. Hopefully I can tip it in faster than it burns through it...
Made a billet breather too
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 25, 2020, 20:43:46 PM
Plumb up the exhaust.
Custom tuned to get peak hp @6350rpm....I think..... pop
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 26, 2020, 12:30:58 PM
Engine cover fitted.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 26, 2020, 12:32:45 PM
Pop up cleat on top of transom.
Handy for towing broken down seadoos, suzukis.....and possibly Daewoo.... st
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 26, 2020, 21:04:08 PM
Make a start on wiring.
Pretty basic system, CDI for spark and seperate ECU that controls advance.
I just unplug the grey wire to disable rev limiter... ::)
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 29, 2020, 19:40:35 PM
Wiring up the dash.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 29, 2020, 22:11:28 PM
https://youtu.be/YDXrPai-xeE
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 30, 2020, 08:06:20 AM
Seems to run pretty good.
A bit quieter and a lot smoother than I predicted. I guess more cylinders smooths things out a bit. I'm still not sure of the exact firing order but it's a 90 degree v6 as opposed to the more common 60 degree v6. Not sure on mr Yamaha's reasoning behind it? Above my pay grade....
Title: Re: 2 stroke comeback.
Post by: quattro on June 30, 2020, 08:23:20 AM
Sounds mean

90 degree v6s because they made 90 degree v4s. Although omc did make 60 degree v4s along side 60 degree v6s and 90 degree v6s. The 60 degree v4s are very compact
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 30, 2020, 08:27:27 AM
Seems to run pretty good.
A bit quieter and a lot smoother than I predicted. I guess more cylinders smooths things out a bit. I'm still not sure of the exact firing order but it's a 90 degree v6 as opposed to the more common 60 degree v6. Not sure on mr Yamaha's reasoning behind it? Above my pay grade....

Should get a lot quieter with water running through it as well?
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 30, 2020, 09:50:05 AM
Yeah a lot of the parts are interchangeable between the v4 115/140hp v4 Yamaha, pistons, carbs etc. Makes parts availability not too bad.
Will be quieter with water for sure. Dont want it too quiet though. This is the Banshee of jet boats...
Few bits to finish on pump then I can test run it.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 30, 2020, 20:34:09 PM
Put floor in, foot throttle.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 30, 2020, 20:36:02 PM
Electric trim. Switch on steering wheel and trim gauge.
All the mod cons (for a hardcore adventure boat)
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 01, 2020, 19:28:50 PM
https://youtu.be/6BU7-i1efp8
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on July 01, 2020, 21:41:03 PM
Looks good Jeff! How does it jump out of the hole?
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 02, 2020, 07:25:32 AM
Quite a few teething problems to sort through.
Couple water leaks on engine, bolts missing, pop off gasket missing.
Not charging, not sure if regulator, stator or wiring,
Tacho bounces around, could be sign of bad stator/wiring?
Engine bogs off idle, is inconsistent, surges. If idle for too long it bogs really bad.
Carbs getting fuel standoff much above half throttle.

I suspect I'm pumping too much water into exhaust chamber, currently all of it including over pressure dump which is quite a lot.
I'll experiment with restricting it and see what difference it makes.
Might make a different exhaust chamber to try as well, longer and fatter.
Title: Re: 2 stroke comeback.
Post by: wad26 on July 02, 2020, 07:36:15 AM
You dont think fuel is pooling in your long swoopy intake at low RPM and then coming through in blobs? This is the problem we have when bolting a carby straight onto the Subaru intake manifold. It caused very inconsistent running  2c
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 02, 2020, 08:55:27 AM
You dont think fuel is pooling in your long swoopy intake at low RPM and then coming through in blobs? This is the problem we have when bolting a carby straight onto the Subaru intake manifold. It caused very inconsistent running  2c

I dont think so but it could be a possibility? Can idle for quite a while out of water and snap throttle it revs quickly.
Need to sort through everything and make sure tps, crank sensor etc are working properly before major re designs..
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 02, 2020, 09:13:42 AM
On a positive note, the 3 minute run I did get in, the hull felt good, and the pump also felt good, hooked up and no vibrations or noise, well none that were noticed above the engine noise and vibrations anyway.... ::)
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on July 02, 2020, 16:35:59 PM
Jeff, you've certainly got your finger on it aye!

Tell us this story...... --<
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 03, 2020, 08:06:49 AM
Jeff, you've certainly got your finger on it aye!

Tell us this story...... --<

Ouch, that looks sore Ross....that's what happens when you stick your finger In a flywheel while engine running.
Never mind, the finger gets the same type of band aid fix as my boat....
Good as new.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 03, 2020, 08:21:21 AM
Made an intake for carbs, they are a bit low and in the unlikely event that I take on water I dont want them.suckung it into engine.
Was a bit hard welding one handed and I contemplated sub contracting it out to mohawk marine or Ross racing but ended up feeding wire with toes for a better outcome.... l-l
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 03, 2020, 08:24:17 AM
Gaskets kept falling off so I stuck them on with sticky silicone.
I'll go find some type of high performance air filter I can bung on the top.
Title: Re: 2 stroke comeback.
Post by: mallyxt on July 04, 2020, 08:45:57 AM
Jeff
What is the water over pressure dump you are using
Looking for something to protect my intercooler when i put the extra stage on my unit
 
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 04, 2020, 09:28:13 AM
I'm in agreeance with the exhaust water volume Jeff. All my eggbeaters over the years of 135, 150 and 225hp have all had less water coming out the exhaust hub than you would expect. Restricting it could be a good start. Or a fully jacketed chamber?
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 04, 2020, 17:50:33 PM
Swapped voltage regulator but still not charging so I'm guessing it's the stator charge coils? Just a 2 phase alternator.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 04, 2020, 17:56:54 PM
I'm getting what I think is a terrible misfire at about 4000rpm. I did get this engine cheap with no spark and a suspected stuffed ecm or stator so spark possibility. Although I have stuffed with a lot of things so could be fuel?
Starts and idles fine out of water, has a tiny flat spot. Not sure if idle on allot not? But in the water if I idle it for too long it bogs badly, like a lean bog, i have to choke it to rev up, then when revs rise it poofs out a heap of smoke and takes off. This leads me to suspect what William mentioned, fuel pooling in my intake manifold? It's got a few bends so possibly it is a terrible intake design for carburettors?
Title: Re: 2 stroke comeback.
Post by: Paul on July 04, 2020, 18:12:39 PM
Weld a stainless pipe with cooling water running through it, across the intake runners - so that it'll keep the runners warm enough that no fuel can condense out.  If that doesn't help, you can just disconnect that coolant flow through the pipe, so the intake charge is not being heated too much.

Don't forget that stainless is really bad at 'heat transfer' (- a lot worse than copper or ali), so it can be fairly warm, without much energy going into the intake charge.
Title: Re: 2 stroke comeback.
Post by: Allen M on July 04, 2020, 19:00:02 PM
I'm getting what I think is a terrible misfire at about 4000rpm. I did get this engine cheap with no spark and a suspected stuffed ecm or stator so spark possibility. Although I have stuffed with a lot of things so could be fuel?
Starts and idles fine out of water, has a tiny flat spot. Not sure if idle on allot not? But in the water if I idle it for too long it bogs badly, like a lean bog, i have to choke it to rev up, then when revs rise it poofs out a heap of smoke and takes off. This leads me to suspect what William mentioned, fuel pooling in my intake manifold? It's got a few bends so possibly it is a terrible intake design for carburettors?
I?d be looking at your exhaust system for a start.2strokes are very sensitive to exhaust pulses.
In the water the engine will be under more load, even when ideling and your engine could be loading up with exhaust fumes from the reverse pulses going on in an overly restrictive system.
Try running it with an open Pipe to eliminate this.
Any self respecting metal fabricator would have a set of tuned and jacketed chambers on it anyway  hhh
Might as well add TPInjection. That will sort the carbs out once and for all B))T
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 04, 2020, 23:04:35 PM
100% agree with Allen M on the exhaust.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 05, 2020, 08:17:13 AM
Jeff
What is the water over pressure dump you are using
Looking for something to protect my intercooler when i put the extra stage on my unit

This over pressure dump valve is factory part on outboard, maintains pressure from water pump. I'm assuming most outboards have a similar setup? It's just a plunger with spring behind it. About 15psi I think, have used brass non return valve as a pressure regulator but you have to keep clean, bits of stick, stones and grass can jamb them open.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 05, 2020, 08:29:25 AM
I?d be looking at your exhaust system for a start.2strokes are very sensitive to exhaust pulses.
In the water the engine will be under more load, even when ideling and your engine could be loading up with exhaust fumes from the reverse pulses going on in an overly restrictive system.
Try running it with an open Pipe to eliminate this.
Any self respecting metal fabricator would have a set of tuned and jacketed chambers on it anyway  hhh
Might as well add TPInjection. That will sort the carbs out once and for all B))T

Quite possible on the exhaust...I have somewhat replicated the factory shape but my chamber is smaller which I think is less than ideal....I made the exhaust before hull so was guessing a bit. Have a heap of space now so can make whatever. The 2x exhaust banks are separated for about 300-400mm so I might make 2x seperate chambers similar to 3 cylinder jetski chambers?  Should be pretty close as I have 2x 1300cc banks of cylinders.
I'll make sure my ignition/spark is good first.
Then re-do the exhaust/s
If it's still a turd I'll look at fuel injection...
Probably more conventional multi point but before reed valves like the injected mercury 300s.
TPI (new KTM dirt bikes) is appealing but harder to get right and then I would need to hook up oil injection to the inlet air to oil the main crank and big end bearings......
Title: Re: 2 stroke comeback.
Post by: Allen M on July 05, 2020, 09:49:56 AM
Yes, a pair of 3 into 1?s would be a bit more practical than seperate chambers and would certainly look the part.
On the TPI front I can introduce you to a man who lives close to you who has successfully converted several two stroke bikes to run a TPI induction system using a Link computer long before KTM got it sorted. I?m sure he would be only to happy to share some of his secrets.
The two of you could be dangerous together. Let me know when you?re up for it. B))T
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 05, 2020, 15:49:35 PM
Yeah I found a youtube clip of local guy testing a tpi fuelled YZ250, looked to be going well. A lot better than my current coughing, spluttering, smoking, rattly, poor performing heap of junk.
I'll rule out electrical faults first as no point trying to upgrade when the basics are not right yet....
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 07, 2020, 08:31:38 AM
Decided to strip and clean the carbs to rule out leaking/blocked jets/needle valves. Easier to pull engine out to do this. Luckily it's a quick job to lift engine out. All carbs, jets  clean and sparkly inside. Would take a big bit of junk to block main jets, they are pretty big, can poke welding wire through them. And there are 6 of them.... jaw
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 07, 2020, 08:37:14 AM
When pulling the engine I had a eureka moment....
Found 2x spare earth wires not hooked to anything. Turns out they were the earths for the voltage regulator and the main CDI unit! No wonder I couldn't get it to charge and the spark was all over the place.
I plunked engine back in, hooked up the earths and it fired up and purred like a kitten. And charging at 14 volts now too.
Ready for another test run  fl. pop
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on July 07, 2020, 08:51:48 AM
That's one of the nice Eureka moments! I reckon bad earth has caused me more grief than any other thing in vehicles- awesome discovery!
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 10, 2020, 08:16:12 AM
Spark seems to be stable now and charging system working as it should but performance is woefully pathetic. I'm only making about 120hp and missing about 1500rpm up top.
After some measurements if appears I got my exhaust terribly wrong so developing a new exhaust system.
Still deciding if I should replicate the factory system exactly or try make something better like 2x seperate 3 cylinder ski chambers to allow for future performance upgrades.
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on July 10, 2020, 08:22:03 AM
The future is uncertain..... do power upgrades now
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 10, 2020, 08:22:48 AM
Never mind Jeff, I'm loving this project. Not often you don't get it bang on. I think whatever way you go you need similar  or more volume/expansion chamber than the factory leg, and minimal water where possible.
Title: Re: 2 stroke comeback.
Post by: Paul on July 10, 2020, 09:33:52 AM
Jeff, two words "forced induction" - you know you want to.....
 fl. B))T B))T
Title: Re: 2 stroke comeback.
Post by: Markg on July 10, 2020, 11:10:29 AM
Jeff, two words "forced induction" - you know you want to.....
 fl. B))T B))T
Seems the only logical thing to do ,Get on it Jeff the fuel consumption is out the window anyway!!!
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 10, 2020, 12:16:08 PM
As much as I am tempted to bolt a turbo to the this thing, I feel i should learn to walk before run. I've already managed to loose 100hp over the factory setup.. ::)
After my technical consultant crunched the numbers it shows how terribly wrong my first exhaust is.
These 2 stokes are a lot more complicated than the 4 strokes...
Title: Re: 2 stroke comeback.
Post by: Allen M on July 11, 2020, 08:26:00 AM
As much as I am tempted to bolt a turbo to the this thing, I feel i should learn to walk before run. I've already managed to loose 100hp over the factory setup.. ::)
After my technical consultant crunched the numbers it shows how terribly wrong my first exhaust is.
These 2 stokes are a lot more complicated than the 4 strokes...
What formula are you using to arrive at these figures? ii
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 11, 2020, 09:47:07 AM
That's not a formula, it's just what I have currently. Length/diameter.
The factory setup has what looks like a chamber setup although the first restriction seems to be the stinger it is still quite big compared to the end restriction (by prop)
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 11, 2020, 18:39:17 PM
While out shopping I found these 2x identical brand new Husqvarna 3 hunny smog chambers at the scrappy....couple rough measurements and they are very close to 3 cylinder ski exhausts...
I can cut, rotate and boogie these together in about 20% of the time it takes to make a proper exhaust that is still a bit of an unknown so I might just go against my principles and bodge up a rangi dry twin pipe screamer just to see what happens.... pop
 
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 12, 2020, 08:49:20 AM
Could be interesting but my first thought is they will be too restrictive unless you go bigger on the outlet. They look to be off a 250 or maybe 300cc single cylinder. I don't reckon they will cope will that much of a capacity increase.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 12, 2020, 09:42:58 AM
Could be interesting but my first thought is they will be too restrictive unless you go bigger on the outlet. They look to be off a 250 or maybe 300cc single cylinder. I don't reckon they will cope will that much of a capacity increase.

Yeah the stinger(tail pipe) is too small but that's the first thing to get chopped back. Effective area needs to be closer to 35/40mm but with water getting squirted into the stinger it decreases effective area so about 45/50mm dia. (Same as 3 cyl ski chamber)
It seems the chamber size stays relatively the same whether doing 1, 2 or 3 cylinders. More related to piston stroke and rpm than capacity.
The real unknown for me is whether to make head pipe to suit front, middle or rear exhaust port?
That's why it's easy to experiment with these as scrap and can cut/hack up without spending $.
Title: Re: 2 stroke comeback.
Post by: Allen M on July 12, 2020, 10:11:13 AM
Being studying your exhaust drawings and from what I can glen the standard exhaust is basically a tuned length straight pipe system into an open chamber. Followed by a muffler box and ending in a stinger pipe which is a pressure bleed to the whole system giving it the required amount of back pressure. All squeezed into a outboard leg. ie not ideal.
This type of system is slightly better than what you get on a weedeater or chainsaw  but way short of a proper expansion chamber on a high performance two stroke motorcycle.
A tuned length straight header pipe will give you a strong reverse pulse needed to make good power but over a very narrow rev range. ie an almost uncontrollable powerband  on a KX 500 motorcycle with virtually no power until it comes on the pipe. Then great gobs of power to spit you off the back.
In an outboard or Jetunit situation the load is more constant so you can tune the length of header straight pipe to match the peak power requirement of your prop or impeller.
Back to your current setup it would appear that your header pipe is longer than on the outboard setup.
This will result in the power boosting reverse pulse which essentially super charges the cylinder  arriving back at the exhaust port after the piston has shut the port.ie your missing out on a heap more power. hhh
The diameter and length of the header pipe is critical and we can be sure that the outboard manufacture has done a lot of homework on this so my suggestion is shorten up the header pipe section to replicate the two pipes in the original system. 2c
Title: Re: 2 stroke comeback.
Post by: powerband on July 12, 2020, 10:42:53 AM
Hi Jeff, I once did a chamber for a customer 3 cly Konig. Your port timing & bore & stroke may be different but this may help. Here are the sections.
Stub=
 20. long   46.
160. long   46. to 64.
80.  long   64. to 90.
200. long   90. to 90.
130. long   90. to 31.
200. long   31. to 31.
I think the Husky pipes will need to be longer in the mid section as well as a bigger stinger diameter.
It would be interesting to see if varying the diameter to a smaller size on your existing pipe would help.

Paul.
     
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 12, 2020, 11:24:35 AM
Thanks for the input.
Gotta love that half imperial, half metric units we seem to work with.... O))))
Yeah, when I study the outboard setup it does appear the first restriction is the "stinger" but it is quite large  and I have never seen an expansion chamber with a double cone setup.
I think Allen is right in that the first chamber is it. Like an aircraft/microlight setup? But the second chamber part is what is confusing me, possibly something do with all 6 cylinders merging in the one place?
3 cylinders can work on one chamber as there is enough degrees timing separation between for the ports to be open/closed before the next ones turn. But 6? I'm not sure?
I cant replicate the factory setup exactly as it's in a straight line (leg) so I cant cut a hole in transom and bolt it o  as my jet unit is in the way....
I can replicate the size/shape but will have some bends in it which may or may not affect the way it works? The way the 2x headers point at the first restriction and shape of it has me wondering??
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 12, 2020, 11:32:55 AM
Does anyone know what the power absorption of propeller is compared to jet unit? (Please don't kick me off the site for asking)
The jet unit is easy, we have enough data to guess close but I believe a prop which is kind of positive drive (not counting the "slip factor" so likely needs a bit more bottom end power to get going?
So I can sacrifice a bit of bottom end power as my pump is not needing it?
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 12, 2020, 12:41:14 PM
I reckon all the scavenging/reverb is taken care of in the valley/powerhead section. I think you need more volume and less water after the powerhead, and although the prop seems like a choke point on an outboard the forward motion creates a big low pressure aiding scavenging.
Maybe try and find info on the Sportjet motors and see what setup they have after the powerhead.
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on July 12, 2020, 13:01:34 PM
Jeff
     This may help. 2 stroke calculator for exhaust design' port timing etc

https://www.youtube.com/results?search_query=%232TExhaustCalc


http://birdcagesoft.com/2tExCalc/index.html


Does this look like what you removed?
http://www.southcentraloutboards.com/99999-04042-00-yamaha-exhaust-guide-1995-2007-200-225-250-hp-2-stroke-29870-ehp

Here,s a V8 with tuned pipes

https://www.youtube.com/watch?v=EmnsXTMLzCE
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 12, 2020, 19:16:57 PM
Manifold to bolt to block. Spigots so I can adjust length of header pipe. Will be interesting to see what difference it makes.
Title: Re: 2 stroke comeback.
Post by: Allen M on July 12, 2020, 19:54:57 PM
Thanks for the input.
Gotta love that half imperial, half metric units we seem to work with.... O))))
Yeah, when I study the outboard setup it does appear the first restriction is the "stinger" but it is quite large  and I have never seen an expansion chamber with a double cone setup.
I think Allen is right in that the first chamber is it. Like an aircraft/microlight setup? But the second chamber part is what is confusing me, possibly something do with all 6 cylinders merging in the one place?
3 cylinders can work on one chamber as there is enough degrees timing separation between for the ports to be open/closed before the next ones turn. But 6? I'm not sure?
I cant replicate the factory setup exactly as it's in a straight line (leg) so I cant cut a hole in transom and bolt it o  as my jet unit is in the way....
I can replicate the size/shape but will have some bends in it which may or may not affect the way it works? The way the 2x headers point at the first restriction and shape of it has me wondering??
When I talked about straight header pipes I meant that they don?t have any taper or very little taper over the length of them.
Replicating them with bends won?t affect the performance of them as they are working like a set of header pipes on a four stroke engine.
Expansion chambers are built with a taper to broaden the rev range that the expansion chamber will provide a benefit to the engine.
The degree and length of each cone has a significant effect on the power characteristics of the engine
A parallel walled header pipe will give you the strongest pressure pulse but over a very narrow rev range. pop
Title: Re: 2 stroke comeback.
Post by: Allen M on July 12, 2020, 20:04:39 PM
Jeff
     This may help. 2 stroke calculator for exhaust design' port timing etc

https://www.youtube.com/results?search_query=%232TExhaustCalc


http://birdcagesoft.com/2tExCalc/index.html


Does this look like what you removed?
http://www.southcentraloutboards.com/99999-04042-00-yamaha-exhaust-guide-1995-2007-200-225-250-hp-2-stroke-29870-ehp

Here,s a V8 with tuned pipes

https://www.youtube.com/watch?v=EmnsXTMLzCE
Great calculator links thanks Warick.
I wish they had existed back when I was playing around with two strokes. All we had was a calculator and a set of tech drawing instruments. Wished I?d paid more attention to maths back at high school . b>
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 13, 2020, 12:57:07 PM
This is what's called an upgrade exhaust tuner, as you can see the exhaust out of the cylinders just exits a narrow cone (2x banks seperate) the race one is just 50mm shorter but the chamber is unchanged obviously. One is shorter than the other as cylinder banks are offset 30mm. So exhausts are the same length.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 13, 2020, 21:31:39 PM
Chopped up the Husky pipes, found these catalytic converter filter thingies inside....puttz, no wonder Huskys are so slow....
I'll not be putting them back in.
Take them back to scrappy, might be able to swap for a Honda engine or something else useful
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 13, 2020, 21:36:15 PM
Bit of trimming, banging and hacking and I have one pipe the right size, shape (i think) and lined up with outlet. As it is now is near identical dimensions as 3 cylinder 1200cc Polaris jetski chamber.  The belly is slightly fatter but I hope that doesn't matter too much? Can always squirt a bit of water in or smack a dent in it...
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 13, 2020, 22:25:41 PM
Looks real good. Will you wrap them or water inject? Double skinning will take an effort!
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 14, 2020, 08:29:07 AM
I'll just wrap them as only temporary to see what will work. I'll squirt water into the stinger but might put some other injection points along similar to what jetski exhausts have.
Some people set up rpm based water injectors on chamber to alter the effective chamber volume based on rpm.
Title: Re: 2 stroke comeback.
Post by: Allen M on July 14, 2020, 10:06:17 AM
Bit of trimming, banging and hacking and I have one pipe the right size, shape (i think) and lined up with outlet. As it is now is near identical dimensions as 3 cylinder 1200cc Polaris jetski chamber.  The belly is slightly fatter but I hope that doesn't matter too much? Can always squirt a bit of water in or smack a dent in it...
A fat belly is GOOD b> will give a stronger mid range. Noise could be an issue but it?ll be good to see if this makes it Howl like a good two stroke should. I suggest you keep the water to a minimum.pop
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 14, 2020, 11:09:23 AM
I can alter the length of header pipe about 50mm as that part is a bit of a guess, went to middle cylinder exhaust port but front cyl is longer header and rear is shorter so must be a compromise. This engine has slightly different port heights and compression ratios across the cylinders (from factory) so possibly this is the reason? The 3 cylinder jetskis have unequal length headers also and I thought if it was beneficial to have all 3 the same length they would be?
Much to learn.....
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 17, 2020, 09:14:58 AM
2x pipes in, one 30mm longer to match the cylinder bank offset. 30mm.
Bit louder than last setup (and that was not exactly quiet.... ???
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on July 17, 2020, 11:09:22 AM
2 Stroke and Quiet in the same sentence  l-l
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on July 17, 2020, 12:23:27 PM
I have been following a few USA builds- one of which is powered y a 240hp sportjet- that thing is stupid loud and frankly unpleasant as its not muffled down the leg like an outboard. Good luck taming the noise in a jet tbh.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 20, 2020, 08:02:19 AM
Seems more crisp with chambers.
Reminds me of the CR500 I used to own....glorious....

https://youtu.be/qJZtZ98PgmU
Title: Re: 2 stroke comeback.
Post by: Allen M on July 20, 2020, 21:56:06 PM
Seems more crisp with chambers.
Reminds me of the CR500 I used to own....glorious....

https://youtu.be/qJZtZ98PgmU
Sounds a lot crisper now  b>
Time to get it wet again  B))T
Hope it?s not too lean though.Be a shame to turn those pistons to ash now. c0H
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 21, 2020, 05:27:29 AM
Goes hard nuts now. I have picked up about 1000rpm.
Getting over 90ks @5500rpm and then I ran out of fuel and had to paddle back to trailer.   
https://youtu.be/yxZWYQgQWM4
Title: Re: 2 stroke comeback.
Post by: Jimmy Jet on July 21, 2020, 07:29:33 AM
Nice one Jeff! Going to get a long way up some skinny.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 21, 2020, 11:33:03 AM
The exhaust chambers have given me about 60-80hp more than my first pathetic attempt.
I think I'm pushing close to 180-200hp currently? Was hoping to hit 6000rpm but at 5500rpm I'm a bit short. Possibly a bit too much pitch in pump to push 6000rpm as that would put speed over 100ks and I doubt I can coax that much power out of it?
It's still a little buggy off idle and I think it's my intake/carb setup.
Bit more testing required....
Title: Re: 2 stroke comeback.
Post by: powerband on July 21, 2020, 22:02:53 PM
Hi Jeff, In the past experimenting with chamber I have found cutting 10.mm out of the header pipe as close to the end as possible will give up to 1,000 rpm more without losing bottom end power. If that does not work put it back in and go to the stinger.  If you increase the diameter by 5.mm you will gain top end but you will lose bottom end the bigger you go. An ETG will let you know if you are rich or lean. I have found that the unleaded fuel is not as forgiving if the motor is on the rich side. You lose a fair bit of power.

Paul.
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 22, 2020, 08:37:21 AM
Yeah I can trim about 20mm out of the header pipes.
As I understand it, the stinger diameter is very important as it holds the correct pressure in the whole system.
I currently have 48mm dia stingers which (on paper) is way too big but I'm injecting water into stinger as well which changes things drastically.
I might alter the water amount and see what that does as it's not a known constant like a fixed orifice.
I have an egt gauge I will mount in one chamber. Although I'm  ot sure what's a normal or save or on the edge of meltdown temp??
Also have a wideband I can fit but I'm guessing the oil will foul it quickly?
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on July 22, 2020, 14:14:17 PM
How easy to fit a pressure  gauge to the pipe and a tap to turn the exhaust water off and see how much exhaust pressure and performance change?
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 25, 2020, 16:43:02 PM
https://youtu.be/0SWU0Ympd-k
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 28, 2020, 10:20:08 AM
Surveying a spare block for forced induction prototype. This is same basic block but the putt bomb 150/175hp version. The block is the same casting but sleeves are different, lower/smaller  exhaust ports. I'm thinking this might be better for turbo use as will get a bit more power stroke and the boost will make up for it....
Likely will just blow more unburnt fuel straight out the exhaust? But I guess a suitably sized turbine at the end of expansion chamber will increase back pressure as boost pressure rises? pop
Title: Re: 2 stroke comeback.
Post by: Allen M on July 30, 2020, 08:27:58 AM
Surveying a spare block for forced induction prototype. This is same basic block but the putt bomb 150/175hp version. The block is the same casting but sleeves are different, lower/smaller  exhaust ports. I'm thinking this might be better for turbo use as will get a bit more power stroke and the boost will make up for it....
Likely will just blow more unburnt fuel straight out the exhaust? But I guess a suitably sized turbine at the end of expansion chamber will increase back pressure as boost pressure rises? pop
I agree with the thinking re the lower exhaust port timing in a turbo application. pop
Title: Re: 2 stroke comeback.
Post by: powerband on July 31, 2020, 10:30:00 AM
Hi Jeff.  With the testing that you have done so far how does it compare to a Yamaha 3cyl 1200cc 2 stroke?

Paul.
Title: Re: 2 stroke comeback.
Post by: Jeff B on August 02, 2020, 11:11:46 AM
Hi Jeff.  With the testing that you have done so far how does it compare to a Yamaha 3cyl 1200cc 2 stroke?

Paul.
Well I guess at this stage it's not a lot different to a well set up  big 3 cylinder 2 stroke? 
I'm getting about 90ks @5500rpm.
The hull and pump are excellent, I feel I'm pretty good there.
The engine ideally I want another 500rpm to really be singing over 100ks
I would be stoked if it went as well as 2x 3 cylinder ski engines but not sure if that's possible from this configuration?
I have other more "sensible" boats to keep me on the water while this one develops further..... pop
Title: Re: 2 stroke comeback.
Post by: Jakedale on September 20, 2020, 06:44:01 AM
I'm building a jet boat with a 1200cc Yamaha here in Sweden. There are a lot of lakes here but No jetboats so i thought i should be the first one to introduce this here 😁 I ran across a Suzuki 200hp outboard and i thought that it would work in a jet boat but never heard anyone doing it and here you are. Thank you for a great thread!
Title: Re: 2 stroke comeback.
Post by: Jeff B on May 30, 2021, 18:10:05 PM
Some more 2 stroke development in progress.
Anyone know the optimum firing order for inline 4 cylinder 2 stroke?
Think I'll do a cross plane crank rather than big bang.
Title: Re: 2 stroke comeback.
Post by: Ross Goldsack - JBNZ Immediate Past President on May 30, 2021, 21:39:07 PM
In the second photo, are you about to straighten it by driving the forklift over it?
Title: Re: 2 stroke comeback.
Post by: LBD on May 31, 2021, 16:21:49 PM
Neat progects going on here....

In the late 70s a guy up in Picton inboarded a 135 Chrysler in a small racing hydroplane, it went well but was just a little too noisy for the driver with a huge exhaust opening next to his head.

But this thread has got me thinking now... I have a 150hp outboard jet pump... I could inboard that with a 150 power head... maybe even leave the exhaust out through the jet.... hmmmmmm I wonder?
Title: Re: 2 stroke comeback.
Post by: Allen M on June 01, 2021, 07:33:11 AM
In the second photo, are you about to straighten it by driving the forklift over it?
He may well need to after the crank has twisted with all that torque going through such a long press together crank. c0H
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 27, 2021, 09:00:03 AM
Some weekend bbq action
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 27, 2021, 09:03:21 AM
The seperate cylinders are pretty handy, does make the engine pretty long though but easier to work on and modify.
Can go 1600cc-1800cc depending on what top end, power valve or non power valve.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 27, 2021, 09:05:30 AM
Clamped a solid chunk of 80mm chrome bar in it. Should keep it straight.....
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 27, 2021, 12:51:10 PM
I now have a nice inline 4 crankcase.
Next job is to use these 3x bung 3 cylinder cranks and make one good 4 cylinder crank.....
Still not sure what's the best firing order??
1342??
1324??
1234??
Title: Re: 2 stroke comeback.
Post by: Paul on June 27, 2021, 14:40:00 PM
Have you split any the crank parts you have? Are they able to be 'clocked' in any position, or are they splined/indexed/etc (giving only certain options available)?

A 4-stroke 4-pot is normally 1342 for vibration and smoothness (piston masses equal& opposite and bending-moment on crank minimised).

Chev V6's run down the crank from flywheel end (654321).

I seem to remember Ford V6's (Essex etc) run down the crank starting at front pulley end, (which due to strange cylinder numbering, is 142536). I think Honda had the same cyl numbering - not sure about firing order though.
Title: Re: 2 stroke comeback.
Post by: Keltik on June 27, 2021, 16:23:03 PM
Crossplane crank for novelty purposes?

I'm sure there's an engineering reason to do it but I just want to hear what it sounds like.
Title: Re: 2 stroke comeback.
Post by: Paul on June 27, 2021, 17:38:21 PM
Crossplane crank for novelty purposes
On a 4-cyl 2-stroke? It would be terrible for vibration.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 27, 2021, 18:00:26 PM
On a 4-cyl 2-stroke? It would be terrible for vibration.

I will have to have cross plane crank if I want even 90 deg firing order....
That was the plan....
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 27, 2021, 20:39:09 PM
Crossplane crank for novelty purposes?

 

I am now fully aroused....  pop cou
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 28, 2021, 06:34:42 AM
Am I missing something here? What's good about a crossplane crank? It's just the firing order....
I don't really want to go flat plane like a 4 cyl 4 stroke as that will be firing 2x cylinders at same time.
I'm not sure why Yamaha did it on their R1? It just makes an uneven firing order and sounds like a v4...
Title: Re: 2 stroke comeback.
Post by: Paul on June 28, 2021, 10:37:49 AM
Crossplane only really makes any sense on a 90degree V8.

I don't really want to go flat plane like a 4 cyl 4 stroke as that will be firing 2x cylinders at same time.
I'm not sure why Yamaha did it on their R1?

Smoothness and vibration - controlling the opposite mass-oscillations.
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 28, 2021, 15:19:40 PM
a good explanation of the relative merits.

https://www.youtube.com/watch?v=-s5bSQIQQsY&ab_channel=EngineeringExplained

Title: Re: 2 stroke comeback.
Post by: Keltik on June 28, 2021, 19:14:13 PM
One consideration for your crank phasing could be running dual expansion chambers with cylinders paired together.  I think snowmobiles might do that kind of thing
Title: Re: 2 stroke comeback.
Post by: Kakapo76 on June 28, 2021, 19:15:15 PM
Hey Jeff,

I found a channel you might find interesting/ useful- got some cool experimental 2 stroke tuning stuff.

https://www.youtube.com/channel/UCHRXYmO1vdp-Bi1-w11R7WQ
Title: Re: 2 stroke comeback.
Post by: powerband on June 29, 2021, 13:14:02 PM
Hi Jeff,
The Yamaha TZ750 straight 4 is 1&4 TDC then 2&3 TDC. Folan, a Swedish engineer built a 1,000cc twin both @ TDC for torque, then split crank to 180 for power, fast or slow tracks for MX sidecar racing.
Paul.
Title: Re: 2 stroke comeback.
Post by: Jeff B on June 29, 2021, 13:30:18 PM
Hmmm interesting, weren't the TZ 700s and 750s in essence 2x TZ 350s joined together? (2x seperate cranks)
I guess glavine 1,4 down and 2,3 up @ 180 deg will be the best for balance but I'm not sure if the crank will like firing 2x cylinders at once?
All the 2 stroke 4 cylinder outboards seem to fire at 90 deg evenly (cross plane crank)
And I think that would sound better,?
In motorcycles, the "twingles" always sounded a bit off....
Title: Re: 2 stroke comeback.
Post by: orac12 on July 08, 2021, 10:55:03 AM
I think there is a couple different theories in the motorcycle world to do with big bang or screamer firing order setups. The big bang, giving more time for the tyre to relax and regain grip between combustion cycles.
Where as a screamer the combustion cycles are evenly spaced and provide more consistent power.

Not sure how it would affect a jetboat,big bang firing order might be hard on splines ? 
Title: Re: 2 stroke comeback.
Post by: Jeff B on July 08, 2021, 11:02:11 AM
I think there is a couple different theories in the motorcycle world to do with big bang or screamer firing order setups. The big bang, giving more time for the tyre to relax and regain grip between combustion cycles.
Where as a screamer the combustion cycles are evenly spaced and provide more consistent power.

Not sure how it would affect a jetboat,big bang firing order might be hard on splines ?

Yeah that's what I believed also.
An even firing pulse always seemed like a better option to me.
I'm not sure why Yamaha adopted the cross plane crank for their R1? Lots of mumbo jumbo about torque transfer and traction but I just cant like the sound it makes Haha.
I dont need uneven torque pulses or traction aid.....I hope....
Title: Re: 2 stroke comeback.
Post by: orac12 on July 08, 2021, 13:02:39 PM
I think the smoother output of the screamer setup would be the way to go in a jetboat.
Title: Re: 2 stroke comeback.
Post by: Warwick Marflitt on July 09, 2021, 07:52:17 AM
Next project will be 9 cylinder radial powered Gnome style engine...with a stationary crank,the block and cylinders all rotating en mass!! Jeff's trickiest waterjacket creation yet???
Power strokes evenly spaced across the cranks duration is more linear and smoother than twin firings at 180.... imagine a two pole electric motors power/torque delivery?? And then a 30 pole/cyl = one power stroke/push every 12deg of crank rotation probably why the Americans built the 36cyl 127litre  Lycoming XR-7755 5,000hp radial... hi-