Low RPM New Prop or Motor Problem

[stonephoto]

I have a 1992 Seafarer with a 1993 Yamaha 225 on an engine bracket. I'm only getting 4100 RPM at best at WOP. That's about 28-29MPH. The engine seems to run really well and it does plane nicely. The manual says I should get 5000-6000 RPM. My stainless steel prop is a 14 1/2 - 17. Do I need a different prop? Should I be happy with this RPM considering it's probably getting better gas mileage? Is there something more seriously wrong with my motor? Any suggestions would be greatly appreciated.

Matt

 

[Guitar1]

Prop Change.....

Sounds like a different prop is in order. I would suggest trying a few different sizes before you commit. The motor needs to run near it's max rated rpm.

If you decide to sell your current prop let me know....

Thanks,

Guitar1

 

[uncljohn]

I run my OX66 at about 3900-4200 rpms at cruise, and go 28-30 mph. I CAN push it to WOT and get 5300 rpms, but never run at WOT. Just b/c a boat can achieve max rps doesn't mean you should run it at that level. I can tell from the engine sound when it goes from a purr to a whine....right about 4400 rpms......and she likes to purr....

I think based on your stats that you are achieving 'cruising rpms' when the throttle is WOT, which means our throttle needs to be adjusted or you need a different prop. I don't know what size prop I have.