Kiwiprop

[capbill]

When I installed the prop last winter I gained .5 to .75 knots boat speed, better rudder reponse but lost ~1 knot speed under power with the 39 hp Yanmar. It tops off at 7+ vs. 8 knots at max rpm. Has any one increased the factory set pitch and if so how much?

 

[JohnShannon]

I think if you look at the Kiwi prop site they do admit that you could lose some top speed.
How is the vibration? How is the backing?

 

[capbill]

Yes, since the total area of the blades are less, the effective thrust and efficeincy will be less. I sent them a concern re. cavitation but they returned that I could increase the pitch untill the rpm drops which is the sign of 'overproping'. Do you have a Kiwiiprop?
All the special prop makers say that theirs is the best compromise but I am satisfied with the Kiwiprop. I am looking for someone that has direct experience with their application.
Ther is no increase of viberation vs. the fixed original. the pitch in reverse is higher thus more rpop walk but knowing this is not a problem.

 

[JohnShannon]

Well I think I am going for one. My existing prop is a two fixed two blade and I suspect a poor match for the motor (Volvo 2003 28hp) I can rev to 3500 rpm (too fast I know) with no black smoke.

So I could use more prop. The Kiwi is 3 blades so more area should develop thrust at lower RPM even if the shape is slightly less efficient I hope to get less vibration, I hope the feathering will increase sailing performance.

In my quest to improve the boat I am now wondering about drive savers, these are supposed to reduce vibration, although the change from 2 to 3 blades should do that anyway. Does anybody have experience with drive savers?