Prop Question

[nautme]

I recently bought a 20' aluminum pontoon with a bad motor. I took the motor (1970 60hp johnson) off my old dilapidated 16' trihull and put on the pontoon. The motor now does not seem to reach full RPM @ WOT. The pontoon has a tach, but I don't know how to hook it up (the old boat didn't have one). I don't know what pitch the prop is, but am pretty sure it is the one that came with the motor originally. I was told I probably needed to change props. When on the trihull, I could run 30-35 mph, on the pontoon only about 12-15. I know I'm not going to get the speed of the smaller boat and I usually just putter around anyway, but was told I need to run the motor at WOT every so often to help "clean it out". Any suggestions?

 

[Barnacle_Bill]

Re: Prop Question

Tach required 12VDC, a ground and the grey wire from the harness is it's feed. This grey wire originates at one of the yellow wires that comes from your stator and also feed the rectifier.

 

[steelespike]

Re: Prop Question

You really need to know what your present prop is.And you need to know what rpm you are running Then you can tell what prop you need.If your prop was good on your tri hull you will definately need to go lower on the pontoon.

 

[nautme]

Re: Prop Question

If your prop was good on your tri hull you will definately need to go lower on the pontoon.

I "THINK" the present prop is a 17 pitch. By lower, do you mean a lower number? How much lower?

 

[steelespike]

Re: Prop Question

My guess is about 12 in. pitch.