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In an earlier post I stated that boat speed was a function of engine horsepower and if you put a large horsepower engine on a boat, the speed increase was a function of the horsepower ratio to the cube root (all other things considered equal such as boat weight, boat load, gallons of gas, etc. Engine weight would increase with the larger motor). One Guest disagreed with my thinking. Here's the formula I had in mind:
Top Speed 2 = Top speed 1 x (HP2/HP1)^0.3
Meaning the new speed is calculated by taking the ratio of the new HP divided by the old HP to the cube root times the old top speed.
I don't think this would hold up for cars or motor cycles, just boats.
What do you think is the correct answer? Maybe for planing hulls I should be using the square root? What do you think?
Top Speed 2 = Top speed 1 x (HP2/HP1)^0.3
Meaning the new speed is calculated by taking the ratio of the new HP divided by the old HP to the cube root times the old top speed.
I don't think this would hold up for cars or motor cycles, just boats.
What do you think is the correct answer? Maybe for planing hulls I should be using the square root? What do you think?