Prop info ...

[Joe Fox]

I have an Irwin 31'' sloop with a 15 hp Yanmar engine. The boat has a 2 blade prop, 13 x 13 x 7/8, 3200 rpm @ 6.5 k. I would like info for a 3 bladed prop to increase the speed and performance.

[Denr]

To increase speed and performance I would suggest a new full battened main (5-7 oz. material) and perhaps a tri-radial 150% genoa; personally, I like the products from North.

[paulk]

6.5 knots sounds pretty quick for a 15hp engine on a heavy 31 foot boat. Changing to a 3-bladed prop might add a little speed under power, and it might not; the engine is only so powerful and the boat''s weight isn''t being reduced. The three blades could easily cut sailing speed by half a knot in all conditions. For water-skiing, you''ll need a different boat.

[windship]

First of all, I agree with Denr''s point.If six and a half knots isn''t enough, get a power boat.
I don''t think your going to do any better.A three blade prop will not give you more speed, but it will move the boat better through wind, seas and currant.Personaly, I think that with a fifteen horse engine and a displacement of nine thousand three hundred,(which is light for a thirty-one footer and IS the reason your getting six and a half)your lucky to be getting the six and a half

Dennis