1997 Force 90 Hp r.p.m

[George.K]

Hi

I have a 1997 Force 90 HP and i wonder if i have the correct size of propeller. When i bought the boat,the propeller on the engine was 13'' x 19 pitch and the r.p.m was 5800-6000 at w.o.t.

I change the propeller with new one 12&3/4'' x 21 pitch know i get 4800-4900 r.p.m at w.o.t.

A guy told me to return to the old propeller because the new one will cause my engine blow up.

Any advice?

Thanks

George

 

[George.K]

Re: 1997 Force 90 Hp r.p.m

Forget to mention that the engine service manual write that the normal r.pm must be between 4750-5250 r.p.m

Thanks

 

[Frank Acampora]

Re: 1997 Force 90 Hp r.p.m

Neither prop will "Blow up" your engine. The 90 HP is perfectly capable of turning well over 6000 but fuel mileage will suffer and there will be some slight additional normal wear over what would be expected if you run at full throttle all the time. In fact, I had a 4 cylinder 120 on a small hull that I ran at 6000 RPM all the time. The second prop has your engine turning right within the specified range and that is acceptable. Just keep her at 50-1 fuel/oil ratio and you will be fine.

What boat is the engine mounted on to be able to turn a 21 pitch prop at the correct RPM?

 

[George.K]

Re: 1997 Force 90 Hp r.p.m

hi Frank

It's a 1997 Bayliner 1702 LS

 

[jerryjerry05]

Re: 1997 Force 90 Hp r.p.m

It sounds like either prop will work.
Either prop stainless?
I tried to improve the performance of my boat.
21 center console/twin 85's
I had 17p and thought 19's would give me better peformance.
They did, about 3 mph.
Also the motors used 20% more fuel.
Fill the tank.Go for a spin.
Keep records of speed/distance etc.
Then do the same with the other prop.
Go the same route and speeds.
Then fill it up and see what the usage is.
Or get a 6gal and try burning it up?