PDA

View Full Version : RPMs versus Prop



Garn
06-24-2008, 12:40 PM
A local prop repairman told me that to determine if you have the proper pitch propellor you should be at 4600 rpms at full throttle. Is that correct? My LS only hits 4200 rpm and 39 mph at full throttle. Should I be looking for a different prop?

Garn

GeauxTigers
06-24-2008, 02:00 PM
A local prop repairman told me that to determine if you have the proper pitch propellor you should be at 4600 rpms at full throttle. Is that correct? My LS only hits 4200 rpm and 39 mph at full throttle. Should I be looking for a different prop?

Garn

My Moomba dealer told me that i should be able to hit 5200 RPM @ Full boar with the high altitude props they order for us up here. He suggested the Acme 537 prop.

cab13367
06-24-2008, 03:29 PM
Garn,

What your dealer is saying is that ideally, you want a prop that at full throttle, your engine is right at redline (so you run out of motor at the same time that you run out of prop). In your case, the pitch of your prop is a little too high if your redline is 4600 and you are only getting 4200 rpms at full throttle. If your prop is pitched too low, you risk overreving your engine and you will not get the top speed that your boat is capable of.

Now for wakeboarders or wakesurfers who run a lot of ballast, they are often willing to run the lower pitch prop because it helps the boat perform better when heavily loaded, even at the expense of losing a little top speed. They just have to be careful not to overrev the engine under light loads and high speeds.

If you are mostly a skier, you could benefit from switching to a lower pitch prop. You will improve your holeshot as well as gain some mph on the top end, or at least match your current top speed. Also, I would check with the dealer to see what your engine's redline is vs going by what the prop repairman told you.

Hope that helps.

Al

Garn
06-25-2008, 11:42 AM
Thank you both for your help. I'll check with my dealer.

Garn

zabooda
06-25-2008, 12:35 PM
I think SC has recommended props for their models based on testing but that changes with the higher elevation and requires a different prop. SC should still have a recommendation for those at higher elevation or the local dealer may have modified enough boats to know which prop works best.