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post #18 of Old 04-09-2010
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WOT will vary if you're tied to the dock as the prop isn't moving through the water as it should be and will generally encounter more resistance trying to move the water with the hull not moving.... so will reach a lower max RPM.

Originally Posted by lancelot9898 View Post
Using a photo tach is a good idea since my tach was out of calibration with actual readings lower than what I was reading. I have a Perkins 4-108 which was new in 1985 and I've been basically running with a too low WOT for the past 25 years so I'm not really sure how dire the consequences for over proping is on engine life. I do agree that approx 80% of WOT setting is a good number for cruising and saving on fuel. I also noticed that WOT varies with current. Tied at the slip my WOT setting is around 200 rpm lower than when I'm in open water. One thing I want to see is how this setting changes with current. My theory is that going against a current, my WOT rpm will be higher. How much is the real question. I do have a max prop and have varied the pitch to see how performance changes. FWIW WOT rpm is 2300 rpm and I cruise at 2000 rpm making 6 plus knots with a 37 ft Tayana.


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Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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