Colorado 2nd stage impellor?

[Tripleaj]

I have a J52 Hamilton Jet boat with a Holden 308 and a Colorado 2 stage.
The jet has a Southern Jet 19 degree s/s long type 3 blade bullet impellor, the standard rear (19?) and a 96mm nozzle.
The boat is pretty good pulling out of the water but find it is revving too much to maintain speed when loaded and/or towing.
I am looking at replacing the 2nd stage impellor and am getting mixed responses in terms of what pitch to go.

Some say a 22-23 degree s/s 3 blade with around a 105mm nozzle works well in my situation whereas others have said to only go 20-21 degrees.

Getting up to $100 variation on impellor pricing between NZ suppliers also.

Any thought or help would be appreciated as it cost around $80 freight to OZ to try a new impellor so hoping to get it right straight up (??).

[mohawk]

105 seems big for a 2 stage ?? but changing inserts is no big deal .
Check your O/Ds and the condition of the blades you have first , then if you buy a blade get what the dealer tells you you need.
Pitches recomended are specific too the manufacturer and any reputable NZ suplier should be able too sort your problems over the phone.
Make sure you tacho is accurate too and your second blade isnt in backwards .

[Paul]

Check your O/Ds and the condition of the blades you have first
Make sure you tacho is accurate too and your second blade isnt in backwards .

Yup, what Mohawk said.

Then before buying any blades, try reducing nozzle diameter by 5-8mm.  You can make 'nozzle inserts' from pieces of PVC drainpipe that have been cut/split/shaped, then maybe buy a proper insert, to whatever size you work out is best.

[JohnR]

How much clearance between your impellor and your wear ring. You can use a light from either side (nozzle and grill) to see ruffly how much clerance you have. Anything more than 1mm each side will reduce performance. And 2mm and ull rev heeps and hav less boogey,  you dont need to buy any impellors. If your ods are bad. Get them fixed and if theres still too much revs get the same person who did your ods to repitch your back blade a degree or 2. A new blade aint always the greatest fix. Unless its a 3 bladed bullet up front. Theyr worth it.  I used to have a 108mm nozzle with 18bullet and 19 4 blader rear with plenty of overlap. Then i changed to a 3 bladed fancy pants19 rear  and it didnt grip well or turn very good on 108mm and i went to go down to a 100mm nozzle.  Performance is bugger all difference, may have gained a wee bit of top speed.  But holeshot not quite as good as it was. So spent 650 bux for bugger all


If i opened my nozzle holeshot would increase and top speed would drop and id be back at exactly where i was with the original 4 blader so me buying a new rear blade was dumb.
I know your talking about going up a few degrees so this info is slightly irrelevent to you, but i think my lexus would make the same sort of power as your 308 so surely itd need the same sort of blades.

I have noticed with my smaller nozzle tho that steering slightly lighter also

[Tripleaj]

My OD's are pretty tight and I have made some Nozzle inserts to try.

I was looking into repitching but don't know anyone in AUS who does it so have to spend $80 freight each way to NZ just to try it.
Anyone know who might do it in AUS?

I have the original front impellor to play with. Are they able to be used in the rear?

[JohnR]

Yup. If its not a bullet impellor itl fit. surely theres a engineer in australia that can bend steel. Print yourself of a impellor pitch guage. Its on here somewhere. Measure your pitch as it is now and get a engineer to bend it up a couple degrees. Also what rpm is it rinning at the moment at full noise

Also with nozzle size. Generally more power the smaller the nozzle. Maby you need to go down a few sizes. Get a engineer to make a insert for your nozzle down say 98 and try it and if holeshot sux lathe it out 1mm at a time till your happy

[JohnR]

Also make sure yourblades are in the right way

[Jeff B]

If you pitch an impeller up a couple of degrees the OD's should also be built up/machined as there will be more clearance.
Pitching it up will reduce WOT revs and cruise revs.