What size prop do I need

[pauljr26]

"20 ft pontoon with 1986 70hp

"20 ft pontoon with 1986 70hp johnson, what prop do I need?"

 

[jnscherr]

I have a 1983 70hp with a 13 1

I have a 1983 70hp with a 13 1/4*17 and runs just fine. Depending on your load you might have to change the pitch to aquire the rpm's. Good luck!