[Public-List] selecting prop for new Yanmar 3YM20

[John Scott]

Hi All:

No responses thus far on my earlier query (April 19) regarding new  
prop selection.  I need make a choice and in the absence of  
contradictory recommendations I will likely go with the three-blade  
13X12.  A little update, Claude at Bay Shore Marine, who sold me the  
new Yanmar, clarified that while under sail I should have the  
transmission in reverse to lock the prop so that I wont wear out the  
clutch (as I would if I kept her in neutral to reduce drag).  My  
earlier posting, for which I would still welcome comment, was as  
follows:

Hi All.

I finally made my decision and made the swap from Gray Marine to  
Yanmar diesel (21 hp 3YM20).  Then I got the shock of seeing the  
recommended (optimal) prop choice, a three blade 15X10 (with the  
KM2P-1 gearbox ration of 2.62 in forward).  It’s huge.  Although a  
13X12 is acceptable, that’s still pretty big (and as I understand it,  
it can't left in neutral to reduce drag when I'm under sail because  
the transmission won't get lubricated). An up side is that with a  
stainless shaft I can keep the old shaft tube and stick with the 7/8  
size.

For any of you with a 3YM20 (@ KM2P-1/2.62) what is the prop you’ve  
selected and what has been your experience?

Thanks

John Scott
Wooshkeetaan #26





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