Yamaha 115 running High RPM's

[franco33947]

I have a 97' Yamaha v4115 with a 13 3/8 X 9 ss ballistic prop. I am running at 30 mph with 65 rpms. Motor sounds great and runs excellent. When I am in idle speed it does shake a bit. My prop does have a small ding on one blade and a chip on the middle of another blade. Would this be cause for what is happening?

 

[robert graham]

Re: Yamaha 115 running High RPM's

6500RPM's is high, the range on the engine should be in the 4500 to 5500 range, I had a 115 HP Yamaha and used to trim it out for maximum speed at 5800RPM. Sounds like you need a different prop to get your RPM's back down in the 5500RPM range before the motor loses a piston/cylinder.

 

[Casco Bay Outrage]

Re: Yamaha 115 running High RPM's

You definitely have the wrong sized propeller on the motor.

Do not run the engine higher than the recommended wide-open-throttle (WOT) rating.

I would guess a 13.25 x 17 Yamaha K series prop would be a good one to start with.

If the WOT rpm's are still too high, go to a 13.25 x 19K Yamaha. If too low, go down to a 13.25 x 15.

If you change propeller brands, the sizes are not the same and will take more trial and error.

 

[southtexas]

Re: Yamaha 115 running High RPM's

17 pitch is what I put on mine. 3 blade aluminum 13x19 was lugging at WOT 5200, 13x15 (4 blade ss, 15 was theoretical pitch) would over-rev it. 4 blade ss 17 pitch (theoretical) keeps it in range.