28' Pontoon with 3.0 Mercruiser Prop

[tr@v1s]

Hey all,

I have a 1989 Harris 28' pontoon with 3.0 mercruiser. Current prop is 15 1/2 X 15 stainless. Seems like the recommendation is to stuck with aluminum props on mercruisers from what others have told me. The previous owners had switched to this prop because he damaged the aluminum one. Considering going back to aluminum, but not just because it is stainless.

There are performance questions that will help determine what I decide to do. So, here's what I've observed:

1. I never achieved over 4,000 rpm (read in mercruiser forum that I should be at 4400 at WOT)

2. Max speed is 23 mph (using gps)

3. Pulling a 3 person (Super Mable) tube with about 600 lbs on it (I know that's overloaded by about 90 pounds according to the tag) I still achieve 22-23 mph relatively easily (just no faster no matter how long we run).

So, do I need to go to another prop to get to 4400 at WOT? Should I be able to get any more top speed out of this barge with a 3.0 considering that it tows at the same speed it runs without anything behind it?

Educate this guy please.

Attaching pic of prop.

 

[Scott Danforth]

check your compression and the health of the motor as first order of business.

compression should be between 140 and 150 psi for a healthy motor

If your motor is healthy, you most likely need to drop in pitch for lightly loaded to get to 4400-4600 RPM.

you may need to drop in pitch for pulling the tubes. for your pontoon, I would consider dropping down to a 13p

I used to have 3 props on board with my 3.0 16' boat to cover the need between watersports and cruising

No, you probably wont get much more speed without a lot more motor, lifting strakes and a center toon log.