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Author Topic:   13' 25hp prop sugestions
tugboat posted 03-06-2001 12:27 PM ET (US)   Profile for tugboat   Send Email to tugboat  
Just bought a 1970 13' BW with a 25hp 1970ish Johnson (the shroud is white and the rest is green). The prop needs repair and was wonder if I should consider a new prop. If so what pitch would you guys out there recommend for this boat. The boat will be used by my 3 boys(hence only 25hp for now)
The engine appears to be in good condition having recently been serviced the the compression is 130 and 132 for each cylinder. BTW This site has been a fantastic reference for me and I appreciate all your responses.
jimh posted 03-06-2001 08:25 PM ET (US)     Profile for jimh  Send Email to jimh     
Picking a propellor pitch depends on a few variables:

--prop diameter
--horsepower available
--lower-unit gear ratio
--boat size
--boat loading

Typically for motors in the 25 HP range there are not a wide range of prop pitches available. One or two different props generally serve most applications.

An accurate engine tachometer is essential for determining propellor suitability. You want a prop with small enough pitch to allow your engine to reach maxiumum rated RPM at wide open throttle.

First I'd invest in a Tachometer, then see how the current prop was doing vis-a-vis maximum rated engine RPM at various loads.

Load can make a big difference, especially with lower horsepower engines. Running with just one person, no canvas, and little fuel will be a much lighter load than running with 3-4 people, canvas top up, two full tanks of gas. You have to pick the propellor to match the situation you use the most.


tugboat posted 03-07-2001 11:16 AM ET (US)     Profile for tugboat  Send Email to tugboat     
Thanks Jim I agree with all your points but I was was curious if there were any unique Whaler issues such as it's relativily heavy weight and unique hull shape make prop selection different than a standard OEM.At $65.00 ea I am trying own a few props as possible. Thanks.

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