Propeller pitching for a 37' Hunter Cutter

[TJ-LJ Champion]

What is the recommended pitch and diameter on the propeller for a 37 Hunter cutter rig? Anyone have opinions on what suits this vessel? We have contacted 6 different manufacturers and experts on this subject with diameters ranging rfom 15" with a 15 pitch to a 16" diameter with 7" pitch. Our problem is we're unable to achieve an the designed RPMs of 3600 while under load(2800 max). Engine readily excellerates to maximum governer setting without load.Engine also exibits black smoke and after ruling out injector and timing problems, should be indicative of engine being over propped. Vessel currently is turning a 15 x 15 wheel. Engine is a 44 HP Yanmar. We would appreciate any assistance you can offer.Many Thanks,Laurie and TJ

 

[Steve Dion]

Prop shop not a mfg.

You need a good prop shop and not the mfg. They have computers to calculate these things.One major factor in selecting a prop is tip clearance. I doubt that a 16" prop would work properly on this vessel, otherwise they would have installed them at the factory.You will need to know the engine HP, transmission reduction ratio, shaft size and possibly the weigh of the vessel.I would contact Kilian Prop and ask them what they think. These guys are very knowledgeable and can help you out. Kilian Propeller Tel: 510-614-0596 Regardless of who you purchase a new prop from, be sure that they are willing to take it back and/or replace it with one that will work properly.

 

[Idratherbesailing]

Propeller for a 37 Cutter

If you can post some information about your boat, I'll use the Boatdiesel.com calculator to get an estimate...from basic calculations using my estimates, it seems like you might be overpitched. Need the following infoDisplacement, WLL, Max Rpm (3600?), cruising rpm, and most important, transmission ratio (2:1, 3:1?), and hp at max rpm (44?). If you have these you can use a calculation formula.Some boats are purposely overpropped...my Gulfstar 37 has a 15x12 3blade...this boat is overpropped, and in fact the Perkins engine is overworked at any rpm above 2500...I cruise at 1800 rpm at about 5.5 kts...not efficient, but this is the way the boat has been for 27 years, so...I have a 2.1:1 transmissionratio. $25 spent on boatdiesel.com will let you play with the tools there, but they are not exactly small diesel friendly, although you can learn a lot there...it is a more useful site for my larger Cummins B engine in a powerboat...I have no interest in the Boatdiesel site, but it is a good source.Another source is Campbell Sailor propellers - they have a lot experience with Hunters and their recommendation for my past boat, a 1980 Hunter 33, a smaller sister of your 37, was spot on and made my boat power much better with its small 2qm 15 hp diesel..you can find them on the web..I think the company is North by West or something like that.