prop?

[phattness]

I have a grummon pontoon boat with a 135 hp johnson but the power head was switched to a 115 hp the motor has no prop and I dont Know were to start... I have had it on the water with a friends plastic adjustible prop and it cavatates badly and only pushes 4000 rpm.. any help (boat 18' weight ?)

 

[steelespike]

Re: prop?

Not an expert but::
I think a 13 "pitch would be a good start see if you can find a dealer that will let you try some props, sometimes they will if you intend to buy.I think a 4 blade might help combat ventilation I think there are some props that are specific to pontoon applications.

 

[phattness]

Re: prop?

the other funny thing I did not mention was the cavitation happend crusing strait but also when you turn right and then when you turn left it would bog down ?

 

[steelespike]

Re: prop?

the other funny thing I did not mention was the cavitation happend crusing strait but also when you turn right and then when you turn left it would bog down ?

Technically you are refering to ventilation.Pontoons are special animals and
prone to ventilation for all kinds of reasons.mostly the disturbed condition of the water from the pontoons.Prop performance/reaction is affected by turning
even in a planing hull just not quite so noticeable.A left turn fights the natural rotation of the prop a right turn makes it easier for prop to rotate.
Get a good pontoon friendly prop and then fine tune the setup.Initially you want the motor trimmed in all the way.Usually trim adjustment will be limited.
You may have to raise or lower the motor vertically to find the best performance.