How fast should an I/O pontoon go??

[ski cat jr]

I have a 24' Fisher two toon barge, it has a 3.0L merc w/ alpha 1 outdrive. I get 19mph top speed. The rpm's are at 3900. I would like to get more speed to be able to ski my teenagers behind it easier. Any advice would be greatly appreciated.

Thanks.

 

[beason]

Re: How fast should an I/O pontoon go??

what prop do you have? what year is the I/O? they changed gear ratios in there somewhere. also how much does the barge weigh?

3900 is on the low side. I am getting 4200ish on my 19ft sea ray ski boat, with a 21p prop. I plan to move to a 19p to get the rpm up to closer to 4800.

 

[ski cat jr]

Re: How fast should an I/O pontoon go??

what prop do you have? what year is the I/O? they changed gear ratios in there somewhere. also how much does the barge weigh?

3900 is on the low side. I am getting 4200ish on my 19ft sea ray ski boat, with a 21p prop. I plan to move to a 19p to get the rpm up to closer to 4800.

It is a '99. I will check the prop when I get home, not sure on the weight either??

 

[rogerwa]

You need to reduce your pitch a couple inches. You n?ed to get your wot to about 4600 rpms. This ic very important tod the health of your engine. Over propping can damage your engine by lugging.

Do this and you probably get more speed as well.

 

[lakegeorge]

Re: How fast should an I/O pontoon go??

I would call the company first and see what they usually put on their boat.
Secondly, Type in..... pontoon boat tests...... on the net and you will find a few boating magazines that have tested dozens of pontoon boats in all sizes & engine configurations, this should also help.
You should be getting a lot more speed with what you have, providing you prop it right.

 

[beason]

Re: How fast should an I/O pontoon go??

mine is a 99 as well. you should have the gen 2 that is 2:1 gear ratio.

once you figure out what prop pitch you have, we can go from there. my guess is you have a 21 or higher prop.

at is, only if the engine is running correctly.

 

[steelespike]

Re: How fast should an I/O pontoon go??

The numbers on your prop will appear near the base of the blades or under the prop nut.
I think you have issues other than a prop.But trhe prop size will herlp us pin it down.
Pontoon speeds do vary from brand to brand but I think you should have speeds over 30
with 135 hp.

 

[rogerwa]

In my view, the speed is secondary. You need to get your engine propped correctly before you destroy your engine. With the normal load you engine needs to spin at it's rated wot rpm. For the 3.0 mercruiser I think that is 4600-4800. Somewhere close to that.

Once propped correctly you will get you max speed provided you don't have excessive slip.

 

[Lawnmedic]

Re: How fast should an I/O pontoon go??

I had a '95 Crest Savannah 25' with the 3.0 Top speed ever seen was 24.9 on GPS with 2 adults and 3 Labs onboard.

 

[ski cat jr]

Re: How fast should an I/O pontoon go??

Okay, my prop is a stilleto stainless steel. The numbers stamped on it are 10315 MI415. I also have a prop that I believe was the factory prop, aluminum 48-78116-C1-15. However, I have tried to put that prop on & it just spins on the shaft after I tighten the nut down. I hope this helps narrow it down.

 

[steelespike]

Re: How fast should an I/O pontoon go??

A 15" prop is in the ball park.
According to my figures you have over 30% slip.if 19mph is correct.
Pontoons sometimes have high slip numbers but 30% is off the chart.
I suspect your speed is not accurate.
Is the speed by gps? Speedometers are known to be inaccurate.
We need to get your rpm right as well.But I think you need to be sure the motor is in excellent tune.Throttle opening all the way.Timed right and advancing as it should.