Outboard jet impellor pitch to HP ratio?

[dreadnought]

Hi, I'm new to this site but I have gaining such a wealth of knowledge in such a short time.
Here the question, Jet outboards propolusion units are manufactored by speciality manufactoring in CA. The bowls come in three sizes that I know of small med and large, I have a 140HP, my buddy has a 90HP, the bowls are the same size and the impellors are the same. My problem is that considering that both motors run about 5500RPM's the water thrust should be the same, the only advantage to the larger motor is is getting to full RPM faster, and the disadvantage is the excess weight. Does anyone know of anyone who sells a larger pitch impellor?

Am I correct in this consept?

[redtech]

you can order differant impellors from outboard specialities but if your turning 5500rpm then you are close to the propper rpm a larger impellor will make you engine work harder and most likely be slower

[dreadnought]

My question is that if a 90Hp can turn the same Impellor at 5500 then my 140 should be capable of turning a steep pitch impellor without over stressing the motor. My hope is to be able to push more gallons per minute and increase speed.

[redtech]

looked in outboard jets book and they list two differant impellers one for the 90hp and a (d) model for the 140hp one impeller may be trimmed to get higher rpm out of it
if looking to run faster have you polished you intake yet

[dreadnought]

how would i go about polishing my intake, and where did you read about the impellor models
Thanks very much for your reply

[redtech]

dreadnougt, i found the information on the impellers in an outboard jet dealer book the impellers for the outboards often look the some untill there right next to each other some are alum. and others stainless some are trimmed for rpm and performance while the higher horsepower isn't it's hard to really tune for the most with out looking else were.
polishing the intake i first heard about by jets skiers.(don't stop reading because i said the "J" word) but those that i've done like the resolts.
1.first pull the foot off an clock the liner to the foot
2.remove the intake grate and ROUND off (not knife sharp) the steel bars that make up the rock guard don't reinstall yet
3.bolt the liner into the foot and notice the seem were the liner meets the foot. grind, sand, polish, this seem smooth so it doesn't disturb tne water flow past it to the impeller.
4.keeping the liner clocked with the foot reinstall on the jet unit
5.check impeller shimming and reinstall the bars
i like to repaint the foot when done, i.ve also take some metal off the foot for better flow, can also smooth out some rough edges in the bowl,expermented with extra holes in exhaust house(more noise ? resolts)

[dreadnought]

Thanks for the info, I will try it this weekend. What do you mean by clocking the sleve? do you mean rotating it one bolt rotation?
You were right about the difference in the pitch of the differnt HP units. I took mine and my buddies impeller and examined them on a bench and there is a deference, mine 140HP is steeper then the 90HP so that makes sense. Also have you heard of this power impeller unit that is bigger 7 5/8 instead of the original 7 3/8.

Thanks

[redtech]

dreadnought, clocking is to marking the liner to the foot so that they are always assembled the some direction or so that these marks always line up when assembled (just a five dollor word for a dime job)