I need to know what the pitch would be for a 70;s 50 hp mercury motor used on a pontoon boat?

This is an 11 spline prop and will be used as a spare. I would like to know what the pitch should be. The boat runs about 20 mph with the one on it, but I have no idea what the pitch is.I need to know what the pitch would be for a 70;s 50 hp mercury motor used on a pontoon boat?
they are usually wide diameter and relatively low pitch. it might be tough to find one for an older motor. try 12 1/2" X 10 or 11". if it's a 24' or longer pontoon try a 9" pitch.I need to know what the pitch would be for a 70;s 50 hp mercury motor used on a pontoon boat?
I know the standardprop for a yamaha 50 hp outboard engine has :

pitch 13 and diameter of prop is 11.

Pitch 13 means :one revolution=themovement of the prop's center moves 13 inch forward.

If the pontoon is heavy you could choose a smaller pitch(e.g.12")so you do not have to force the engine.You would lose speed and gain acceleration.I need to know what the pitch would be for a 70;s 50 hp mercury motor used on a pontoon boat?
Any Propellor shop can tell you the pitch the spare is. I would think 14pitch would be good. You need power not speed. The higher the pitch, the more speed. The lesser pitch, the more power.

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