H34/Westerbeke Propeller Pitch

[Ramsay Selden]

My '83 H34 has the 22hp Westerbeke. I don't know what the propeller pitch is, but I don't seem to get much speed for my rpm. At 2500, I get around 4k and have to push it up around 3000 to get much more (4.5k). Could it be I need a propeller with more "bite"--a longer ratio? With 22 hp, it seems like I'd have enough power to trade some leverage for speed. What do people think? Thanks! Ramsay Selden

 

[Michael Brooks]

Try the obvious first

Ramsey, Had a similiar problem and the obvious was the solution. Got below the waterline and noticed all the little critter's that had attached themselves to my shaft and folding prop blades. Once they were removed I went from 5 knots at 3500 rpm to 6.9 at 3500 rpm. An addtional "no sh#t" was my Moor knot meter was actually .6 knots off from my GPS, in actuality I was motoring at hull speed at 3700 rpm. Try that, let me know how it works.

 

[DJ Dreyer]

Westerbeke/Yanmar

Some 34's came with a 15x12 2 blade prop (mine for one) and some with a 15x15 (what I use now). Hunter used whatever was handy when they build a boat. Doesn't seem to make much difference to them what would be the correct part to use.I would try to clean the prop and bottom before I'd mess with a new prop especially if you motored at hull speed before with the prop you have.Now Yanmar 3GMF 22.5 hp have a red line of 3400. I don't know the red line of a Westerbeke but if I had to go to 3700 to get to hull speed, I think that I would change the prop one day soon.

 

[Geoff McLaughlin]

too many revs for sure

My 34 has a folding prop. I reach 5.5 kts at just over 2k, so the additional 1000 rpm has limited returns, and I think is driving the engine too hard, unecessarily. I had a good guy at Westerbeke on the phone, asking him about engine harmonics, and vibration in rev ranges, and it was him who told me not to even drive the boat for extended periods at 2800, where I used to. When I checked my speed v rpm, I saw that hw was right. Ditto all the other answers - clear bottom, check prop is working, etc.Good luck

 

[Clyde Lichtenwalner]

In addition

When evaluating the performance of your engine be sure that the knotmeter, and the tachometer are at least delivering ballpark accuracy. I note that as my instruments age, I sometimes doubt the accuracy of the tachometer. If what you have is the stock (15X12)two blade, I doubt if you need a different propeller. With a clean bottom and prop, mine commonly cruises at 6.5 knots at 2900 rpm. Hull speed is reached at full throttle. Seems about right to me.