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Old 02-22-2020, 02:25 PM   #45
kchace
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City: Brookline, NH
Vessel Name: Shalloway
Vessel Model: Defever 44, twin Perkins
Join Date: Sep 2013
Posts: 2,260
Quote:
Originally Posted by Soo-Valley View Post
IMHO, what sounds off is you are only getting 7KN @ 2000 RPM with a more efficient 4 blade.
I can only compare to my GB and defer to others with same boat as yours.
With one engine down I was getting 7 knots @ 1600 with 2500 max under load.
Overpropped usually lowers the RPM to attain same speed.
I totally agree! The FIRST thing I thought when I read 2000 to get 7kts is that something isn't right. That's about 110hp (according to the HP graph) to move a 36' boat at *almost* hull speed??!! It doesn't make sense.

As a total guess, I would first check tach calibration, then check the transmission ratio, then check the prop pitch. Its possible this boat has an *underpitched* prop or had a transmission with a higher gear ratio swapped in AND the throttle stop (located INSIDE the throttle control on a FL135) does not allow actual full throttle.

Definitely need some investigation - it doesn't add up.

Edit - another correction - WOT throttle on a FL135 is 2600.

Ken
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