Because I’m looking into diesel electric propulsion, which has more torque.
On 5/23/08 10:10 AM, wrote :
Quote:
In theory, you can select your prop size to be 85% of the distance to the hull. If there’s currently 5″ of clearance with your 20″ prop, you could go as high as 25″ in diameter. In practice, I don’t know how close you can get before you start to get prop noise. At one time I had a two-blade 22″ prop and had no problem. A 20″ prop will start to cavitate at about 1200 RPM. With a 2:1 gear reduction, this translates to about 2400 RPM on the engine. If you go to a bigger prop with the same pitch, you’ll overload the engine. If you try to reduce pitch to get your engine speed back up, you’ll start to cavitate at shaft speeds of about 1000 RPM.
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Why are you contemplating a larger prop?
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Rich Carter
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