Prop Size? Hunter 27 w/ Yanmar 1gm

[johnm5858]

I purchased 3 years ago a 1983 Hunter 27. It has the Yanmar 1gm
Rated at 6.5 HP at 3400 rpm. Max Rpm is rated 3600. I only get about 3000 rpm in forward gear and up to 3600 in neutral. In calm water I guess max speed no sails is 5.5 knots.
The prop I have is 2 blades 13 in dia
10 in pitch. Looking forcomments of other owners with this boat and engine. How is your power, Rpms and speed?
Thanks for all comments -

 

[David in Sandusky]

It sounds like you need reduced pitch to maximize power. The other question is how does your power train perform? How fast will it drive your boat in still water? Are you getting any black smoke as you reach max rpm’s?

In the end, you need a prop shop who understands the design of your prop to answer your question. A competent shop may be able to calculate a desired pitch for your prop, and then repitch it.

The prop design does impact pitch. If I remember correctly, our Campbell Sailor 3 blade prop is pitched at 5, and our 1 GM10 will still not drive it to 3400 rpm. But we are very happy with performance which approaches hull speed in calm conditions.