Prop size

[kmx1968]

What is the maximum diameter prop an A27 will turn?
Thank you

[don123]

Like everything else associated with your boat . . . . it depends. On any boat, I like using the largest prop possible because a larger prop turning slower is more efficient than a smaller prop turning faster

My Lehman/Peugeot powered 27 came with a 15X11 and for my Yanmar repower, I upped that to a 17X12. The 'maximum' size would vary depending on how much tip to hull clearance you're comfortable with. Many say you should keep as much as 1/6th the diameter of the prop clearance to the hull (that would be about 2.75 inches for me) - Others say as little as 10% is acceptable (1.75 inches)

My 17 incher has 2 1/4 inches between the tip and the hull and that's about 1/8th the diameter, or 15%. An 18 incher would 'fit' *but* the clearance would be too tight IMO . . . . your opinion may be different of course. I think an 18 would be close enough to the hull to be a bit noisy in the aft cabin. If I were to fit an 18, I think I would add half an inch or so of woven roving to the inside of the hull in the area near the prop, just to be safe - I may go ahead and do that anyway with my 17, it sure can't hurt anything

I would say a 17 is about as large as you can comfortably fit . . . . some folks would say that's too big and a 16 would be the largest you should use

Don

[kmx1968]

Thank you for the reply. I'm not worried about prop noise,I converted the 27 to a work boat and the 4045 John Deere sounds like a Detroit anyway. I agree about the diameter,I like a large prop on an inboard. I have an 18" diameter on it now,would like to get as close to a 20" as possible. Larger props seem to be more efficient and more responsive when maneuvering,and when kicking the stern around to track in a following sea. Guess I will find out at haulout