Yamaha prop - advice

[timw]

I've never needed to worry about props (or understand all the varieties) before until the weekend when I ran over a huge discarded rope which tore a blade completely off my stainless steel propeller.

Looking at the prop it has "23 M" stamped on it.

Acccording to Yamaha who I called this is a 13 3/8th diameter and 23 pitch.

I'm going to replace it with the same pitch but Steel Developments only have this stainless steel prop with a 14 1/2 inch diameter.

They say I will get a slightly better top speed, and 100 rpm lower at WOT.

Is this likely to be correct? The only thing that worries me here is that the various other threads on props all seem to say that 23 pitch is too high. I've never known any different!

The engine is a 4 stroke Yamaha 225.

Any views would be much appreciated.

[codprawn]

4 strokes are different to 2 strokes - a 4 stroke can swing a bigger prop.

[timw]

Mmmm interesting, I didn't know that so maybe the slightly larger diameter will be OK

[Roy Smith]

We had a 225 Yamaha four stroke on a 7.5 Cobra
We had a yam 23 inch which was great it pulled 6000rpm flat out
we also tryed a 21inch but it over rev the engine
i tried alloy 21 & 23 but not as good as the standard S/Steel
the prop i would swap for is the Yamaha 23 Pro series S/Steel
But for the differance in price we did not think its worth it.
For what its worth Scorpion did prop tests on our 250 four
And again the stanard prop was only a couple a knts slower than a pro series
i hope thats helps
Roy

[timw]

Thank you Roy..will be fiiting it later and see what results I get.

Interestingly the max revs I was getting was around 5500. I wonder if this is not enough?

[Roy Smith]

We where told that you know when you have the right prop as your rev should be about 6000 rpm but 5500 rpm sounds like you have to much prop
Next week at Ribx you can try before u buy ?