On Sun, 8 May 2005 20:38:12 -0700, "frosty" wrote:

Does the hull impact the efficiency of the propeller?

That is, if a certain motor with a certain propeller pushes
a fiberglass boat at 90% efficiency, will that same motor/
prop drop to 85% (say) efficiency behind a pontoon boat?

Or, would it just turn that much slower, at the same
efficiency?

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Both. A heavier or less efficient hull will have more drag
(resistance through the water). This will result in more prop
slippage, and the torque required at the prop will increase causing
the engine to develop lower RPMs at the same throttle setting.