Yamaha prop question.

[snowman678]

I have a Yamaha F100 running a steel (slightly dinged-up) 13" X 17P right now & have an opportunity to pick up an almost new aluminum 12.625" X 21P that I was thinking could at the very least make a good spare. The aluminum is obviously a more aggressive pitch, but I'm wondering if the slightly smaller diameter will compensate for that? I'm thinking it may not allow the full amount of revs for the motor with the more aggressive pitch (which would be better than over-revving)? Would this be true, or am I thinking backwards? Obviously it would be best to try it out on the water, but we're still iced up around here & I don't have time to drive to water.

[Northlander]

I think it may be a bit too much for the f100 but Im not sure. Call Jay Soderbloom and ask him. He should know. http://www.soderbloom.com

[marine_man]

A 21 seems like a bit more prop than your F100 will be able to swing.. it'll work, you definitely will be lugging the motor and your hole shot will also suffer.

marine_man

[snowman678]

Kind of what I was afraid of, I guess if it's cheap enough I make pick it up as a spare, but probably not a good option as a main prop. Thanks for the info.

[RiverBassGuy]

That's a large jump in pitch. Your rpm's will definately drop and your hole shot will be much worse. It would make an ok spare, but you won't be happy with how it performs on the water. The f100 should be running about 5700-5900 rpms at wide open. You will be under-revving with the 21p.

[PerchJerker]

I don't think the 21P would make a good spare, even if you got it for free.

[Minnesota Fats]

You'll lose about 800 rpms at WOT with a 4" jump in pitch (if all else is equal). Under-revving is bad, hard on your motor and wastes fuel. If you are just looking for a spare to get you home in case of damage to your primary prop, look at a plastic prop (like a Comprop). They are fairly cheap.

[VMS]

Not sure on this one...

I'll agree on the approx 800RPM loss with only a 4 inch jump up given all else equal. But...going back to aluminum from steel may gain you some RPM's back, and the fact you are dropping in diameter should give you another 250 or so RPMs back as well.

I'm guessing you will see a drop of somewhere close to 400 to 500 RPMs. Either way, That is a pretty big drop, but not horribly much. If your 17 pitch steel is getting you max RPMs, the 21 pitch could very well put you right in the middle of your RPM Range...not the greatest, but "do-able"

If you get it cheap, I'd say go for it...if it doesn't work out, you can sell that prop or at a minimum, exchange it with someone.

Steve