What size prop do I use on a 1977 75 johnson stinger outboard?

Question

I have a 20' pontoon boat with a 75 Johnson Stinger and was wandering what would be the recomended size prop for maxium performance on this motor?

Answer 1

You want to select a prop that will let the engine make 5000-5500 RPM at full throttle with a normal load.  A higher pitched prop will lug the engine, less pitch will overrev it.

Decreasing the pitch by 1 inch will increase RPMs by about 200 (props of similar design).  A good prop guy can customize a prop to optimize a boat/motor combination but you probably don't want to get too fancy.

That motor came with a 19" pitch prop.  If it's turning 4800 on your 'toon, I'd probably try a 15.

Answer 2

On a 20 toon use a 17 pitch> 15 is a bit flat blade and to much RPM> Unless your carrying a load like using it for a barge>Then 15 will be better>