prop for yamaha 15hp

[Roo]

Just looking at the specs on the net for my 2003 yamaha 15 2 st. and noticed the prop listed was a 10.5" ??? I'm Fairly Sure ??? mine has a 9.75" on it. I'll check tonight when i get home but being new to this game I wondered if someone could explain the difference/effects of alternative prop pitch and diameter on performance. I realise there is a massive amount of variables so to narrow it down just how it would effect my rig is a quinne explorer 3.5 V nose punt.

what do you reckon??? ???

Cheers,
Roo.

[Roo]

checked the prop last night... it is a 9.25 x 11 J. the owners manual says this prop is for the 15D. Mine is the 15F which is supposed to have a 9.75 x 9.25 J.

I'm buggered if I know what this all means? particularly to how it effects my boat. ???

[NQCairns]

Hoo Roo The first numbers designate the diameter and the second the pitch. The letter would be some proprietary designator for cup/rake or whatever.

The one you have has less surface area (because of the smaller diameter) and a blunter pitch than the original equip prop.

What does it all mean? I dont have a real clue on an individual boat and engine but if I were to guess I would say the engine probably spins the prop on it now a little slower at WOT than the orig one but it would still be fairly close.

I think they may have propped it like this so that the 15hp wouldn't bog down much from a standing start relative to the orig prop and also so that you can still reach a fair cruise speed when up and away.
Do you have an issue with the way it performs? or just curious. Cheers nq