Prop advice wanted for 15HP Mariner

Hello all,

1982 Mariner 15hp, built by Yamaha. Still have original alum. prop, looks like it's worn enough to be thin and getting out of shape, although boat (14' Lowe Jon boat) is still running fine. Prop is 9.25 x 10.5

A friend gave me an almost new prop off his Yamaha 9.9, he thought it was the same, but it is 9 x 9. Should I use this or not?

Thanks, Steve

On a 15 horse (or 9.9 for that matter) the difference between a 10.5P and 9P is pretty minimal.

The wide open throttle range on that model is between 4500 and 5500 rpms, so you have 1000 rpms to play with.

I run a 15 Mariner on my 14' Princecraft (utility).

In the spring/fall when the temp and humidity is low and I'm running "light" (under 800 pounds total weight - boat/motor(s)/gas/gear/batteries/passengers etc) I run a 4 blade 11 pitch.

If I'm running a little heavy (an extra passenger) or all summer when the temp is above 80F and the humidity is high I switch down to a 3 blade 9 pitch - just helps the motor breathe the thick air a little better.

In general, you can run anywhere between an 8 and 11 pitch and still be well within the optimal rpm range at wide open for this motor.

So after all my rambling - running the 9 pitch is totally fine - in fact, if it had of been a 15 Merc/Mariner instead of a Yami/Mariner, it would have come from factory with a 9D9P Quicksilver prop as "standard kit"....

Thank you very much for the info and for your time! I'll put it on and give it a try. A great help just to know it won't do any damage.

Steve