Need help with a 3 blade prop for Hunter 33

[Ziya Gun]

Help!I own a Hunter 33 '80 sailboat with YANMAR 2QM15 diesel engine. The engine was in bad shape and I had a major rebuilding done. As a part of the boat overhaul, the mechanics discovered that original 2 blade propeller was cracked and replaced it with a 3 blade propeller. Here are the specs;Before the repairs:Original propeller: 2 blade, 14 x 12, no tachometer on board, have no idea what the RPM wasAfter the repairs:3 blade, repitched 13 x 12, I have tachometer, max out at 1700 black smoke pouring out, in reverse I exceed 3000, in neutral I do 3600.All indications are that I am overpropped !HELP!What is the proper 3 blade propeller for my engine? I am a cruiser and would like to stick with a 3 bladeYANMAR specs:2QM15 , vertical 4 cycle water cooled diesel enginerpm's in forwardcrankshaft 3000propeller shaft 1400 1060 (don't ask me why there are two columns in the manual)reduction ratio: forward 2.142.83reverse2.502.50The engine starts and runs very well, but I am afraid I might damage by overloading it. I do not have a knot meter either, so I used a knot stick ( a spring pulled by a discus trolled behind the boat) and maximum speed was 5.5 knots, with the GPS I measured only 3.7 knots? What shall I do?I would appreciate any help in this matterThank you in advance

 

[John]

PROPPED

You are certainly overpropped. The mechanics should be held at least partly responsible for this as. Perhaps a variable pitc prop would solve the problem? Expensive but may work well. How do you find such a small engine in a 33 ? I have a 34 and would like a bit more size than the 20hp on board.best of luck

 

[Ken]

Hunter 33 Three Blade Prop Pitch

I had the same problem with a three blade prop on my 2QM15 ( 80 Hunter 33). I transferred from a two blade (14X12) to a three blade maxi prop with an adjustable pitch. Started at 14 X 11 pitch which produced 2100 RPM according to the tach and smoked. Changed the pitch to 8 and the RPM went to 2750 with no smoke. Maximum RPM is 3000 for this engine.

 

[Kevin L. Woody]

right Three blade

Dear Ziya:Thank you for your letter and question. I’m afraid we will need to know the installed reduction gear. You have listed the two possible reductions for that transmission. Knowing the current installed one will allow us to help you. The reductions you listed call for two different propellers. Sincerely, Kevin L. Woody