[georgiaboy]

I have a 20' pontoon boat I rebuilt and I have a 1987 Classic 50 45hp mercury on it. I have no idea what size prop it should have. Any ideas to get me close?

[bowman316]

What is on it now? anything?

Somewhere around 13 maybe. between 12 - 15 maybe.

You need to know what your current rpm's are with the current prop.

[georgiaboy]

the prop is a 14" pitch and it turned about 5300 on a 16' basstracker that it was on. I have not put the pontoon boat is the water yet. I guess i will check the rpm then on the pontoon.

[bowman316]

I can tell you right now you will need less pitch, because a pontoon is a lot different than a bass boat.

You might not even be able to plane with that prop, but Go see, and depending on your rpm's you may need to go to a 12 or even a 10.

Every inch you drop in pitch adds 200 rpm's.

[georgiaboy]

thanks, that's good info. i will make change after test run.

[steelespike]

When making your test run be sure to try different trim settings.
You may want to get a 4 blade intended for pontoon use.