Colorado 2 stage nozzle???

[Tripleaj]

I have a J52 Hamilton Jet boat with a Holden 308 and a Colorado 2 stage with the nozzle in the attachment.
I am wondering if anyone knows what brand it is and what can be done about fitting an insert. It appears to be a diameter of 3.75" (95.5mm) at the very tip but tapers down to this only in the last 1/4".
The jet has a SJ 19 degree bullet impeller with the standard rear and from a standing start seems to slip a little as it will spin up to about 4500 rpm. WOT is about 4300ish.
Wanted to try going down in nozzle size to see the difference but am unsure of the options with this nozzle. I was going to make an inert but would also have to drill and tap holes to secure it and the short taper change at the tip makes it a bit difficult (unless I machine it out first).

Any thought or help would be appreciated.

[mohawk]

My southern jet insert measures 102 O/D and My arco inserts measure 114 O/D .
Those are the sizes you would need too bore the noz so they would fit.

Ive had 265 hemi , p76 ,and 4.3 chevs all running 94 - 97mm inserts and a heap of blade combos with no slip ever  .  Machineing for an arco insert is a great idea , but 95 should be close too bang on .
Are your blades sharp and O/Ds good ?

[Tripleaj]

Thanks for the response.
The current nozzle appears to taper down to around 98mm but for the last 6mm where it tapers sharply to 95.5mm, as you can see in the photo. Is that normal?
The OD is 116mm. Are they held in with screws on the end face as I will start to run out of wall thickness to add screw holes??
The front impeller is new and has improved the over rev on take off. At a standing start, what over rev should I expect? Previously I could get it to spin up to 5000 but now it is lower.
Thanks again.

[mohawk]

SJ noz is 119  0/d .... you can screw from the side if you want or the end.
even but a blob of weld too tap into. They dont take much holding
second pic is kodiac with old holes in the side.

[mohawk]

Can skim it with nutec bog and file it out till your happy. Doesnt need to be flash for testing.

[Tripleaj]

Ok thanks. Will have a go once I find some material to use.

[Paul]

Could be useful:
http://www.nzjetboating.com/yabbse/index.php?topic=20104.msg164993#msg164993

[Tripleaj]

Interesting. Given me some ideas as said just to see what size I might need. Then I can buy some material and turn up that size. Thanks.

[Tripleaj]

Made a nozzle insert with a 15 degree taper into a 96mm bore which extended over 14mm. Not sure if this will make a difference from before which was a very short taper from 98mm to 95.5mm. The nozzle now has a 100mm bore with no insert which I will try also.
If work permits, I am thinking of making a 92 and 94 mm insert.
Any thoughts on the effects of the insert and also whether two 8-32 screws are sufficient??
Thanks.

[mohawk]

2mm - 200rpm  as a shot in the dark
the 2 screws should be heaps , but locktite them when your finally sorted.

[Tripleaj]

Struggling to find the time to do testing but just wondering on wedging the Nozzle.

At present, when towing a knee or wakeboarder they always want to go a speed that puts the boat on the edge or just off planing so the boat is straining.

When towing a tube with a centre ski pole they get hammered by the rooster tail unless I lengthen the rope but that seems common??? The wake is also very rough when skiing???

I have two 10" square gas strut mounted stabiliser plates on each side of the back but as they are spring loaded they appear more for stability that bringing the nose down so was wondering on wedging the top two bolts of the nozzle to point it down but am unsure on a starting point.

Any experience with the J52 and this situation??

[mohawk]

Yup , pretty normal.... I used too wedge my noz down for wake boarding . 5deg should do it or more if you want..
 Check full lock when wedgeing down a centre steer noz because the steering ball will slip out if you go too far 

[Tripleaj]

Thanks.
I wedged it what I think was about 3 degrees and it started to effect the steering so I left it at that and it seem to improve the issue. While tubing it wasn't blasting them so bad either.

[daveb]

I"m pretty sure the normal ski/tow rope was 25ft(7mtrs) longer than standard(75ft,I think) when we ski"ed behind jet boats... 30 odd years ago and that was well known amongst jet boaters in the day..ha. Try it