Responding to query # 701, I repowered from a Volvo 2002, to a Yanmar
3GM30F. Much time and energy went into the prop aperature,
deadwood,shaft,and the prop itself.We expected to use a 16 x 12
prop,as the factory did, on this Yanmar.
The aperature didn’t have the “rule of thumb, 20% tip clearence” at
the top, for a 16" prop. So we opened the top and reshaped the
deadwood too.
Upon first try, the 16 x 12, would allow the engine to over rev above
4,000 rpm. I was working with Alameda Prop in S.F… After repitching
to 16 x 11, overreving still an issue. Computer modeling recommended
a 17 x 12 Michigan two blade to match the engine. This prop looks
like Mickey Mouse ears, not the slender 2 blade we tried before. We
were trying to add drag by increasing the surface area, and thus to
properly load the engine. The new Michigan did, but the engine could
only reach 3,200 rpm. They repitched it to a 17 x 10 and the desired
rpm of 3,600 was reached at full throttle. For a two blade, this is a
very strong prop, and pushes Calliste to the max. Since Michigan cast
this prop for us individually, we were able to increase the standard
hub diameter to 2 5/8", so this matched the diameter of the set of
spurs we installed just infront of the prop. I am very happy with the
result. I motor a lot, much of the time on passages when the wind
goes light, and like my fellow cruisers have way overloaded Calliste
with all the bits and pieces I want with me.