Home › Forum › Ask A Member › Johnson PO-15 Prop Size? › Re: Johnson PO-15 Prop Size?
Buccaneer,
Your last response is the one that poses a concern over a good question! The PO depends on diameter for good "push" of the water through the cooling pickup on the gearcase—-especially if you are going to do some idling for any length of time. But if all you are going to do is run faster than an idle it becomes less important. I had a 12 x 12 on my Lyman and it did just OK and I couldn’t get full rpm out of the engine. I found a 12 x 11 and that lit it up. I have a 10" diameter prop that goes great on my aluminum boat but I can’t bring it down to a dead idle and get the cooling I want.
Normal test should include using a tach to make sure you are getting full RPMs.
There are Michigan AM props out there that give good performance also.
George