Precision Propellor/max rpms

[Brian2]

Hello, I just want to recommend Gabe at Precision Propellor in Newburgh NY if anyone needs help. I put a Beta 14 in my CD 28 three years ago and started with a Campbell Sailor prop. The prop was way overpitched on install, I could only get 5.2 knots, and 2800 of 3600 RPMS. Then when sent back for adjustment was way under pitched, getting only 3.6 knots!! and 3750 RPMs. Kelsey at West by North said that was the best he could do (under or over pitch). I was not happy. I found Precision Prop and he adjusted the Campbell Sailor so I got 5.4 knots and 3600 rpms. Yay. But it still seemed wrong, as the Campbell Sailor is supposed to be (according the them that says so at West by North) a great prop, less drag, more speed. I found it not to be so. I sent Precision prop my old Michigan, which they repitched, as it was 13 x 10, and with the new Beta I was able to get only 2800 rpms and a lot of black smoke. Gabe at Precision made it approx 12 x 7, and I was able to get 6.3 knots (with no wind/waves or current) and 3450 RPMs. I was quite happy!! But, the engine manufacturer strongly suggested that I repitch again, as it is really important to be able to achieve max rpms, otherwise the engine is working harder for every rpm. So I sent it back again. Just got it back and on a few days ago. I now have max rpms, and 6.2 knots towing a beat up walker bay 10. I am very happy. Gabe charged me once for the re-pitching, but not for the second time. Shipping only. Beta says not to be afraid to run the engine at max, but I generally run it at about 2800 or so, and get 5.5 knots. And I have more power if needed when I cross the mouth of the mighty Kennebec (if under power). I am very happy with the work Gabe did for me.

[Skylark]

Interesting info. So, what was the final spec? It would be cool to plot your results along with the engine power curve. The CD 28 should have a max hull speed of about 6.3 knots. So, it sounds like you should be pleased.

I may need to update/calibrate my tachometer. I usual set a cruise speed at about 2000 rpm on a Perkins 4.108 for my CD 36. With a clean hull that's about 6.4 knots with the original 15x14 three bladed prop. Perkins has a fairly flat tourque curve.

There is a lot of technical info spread about this forum. Would be nice to collect some of it...