Performance - Top End

[rp]

I have a 22 ft. pontoon with a 40 Hp. motor. It tops out fine when my wife and I are ridding in it, but when I add an additional 3-4 people it doesn't come to full speed.

Almost feels like weeds in the prop, but I've checked it several times and most times that's not the case.

I'm wondering if the extra strain on the engine is somehow causing the prop to slip??? if that's even possible.

Or does it have something to do with people sitting in the front of the pontoon that is somewho effecting the props performance because it's not deep enough in the water???

I purchased the boat used, so I don't have the entire history of the engine, but it runs good, be it for this..
Also, wondering if it's just a limitation of having a 40 Hp
on a big pontoon, and the engine just can't handle the strain?

Anyone had any experience with this condition that can provide advice would be greatly appreciated.

 

[rrhodes]

Re: Performance - Top End

I think you are dealing with several issues. First putting people up front will limit your speed due to forcing more log in the water for your 40hp to push. Then the 40hp itself has it's own limitations.

I have a 25' with a 115hp and when I have 3-4 extra people in the front I have noticed about a 4mph decrease in speed

 

[Silvertip]

Re: Performance - Top End

Look at this way, does your car perform the same with four people in it as it does with just two? Of course not. Weight is drag. And since you only have 40 HP on a 22 footer, it is already straining with just two folks. Adding two more puts it over the edge performance wise.

 

[rp]

Re: Performance - Top End

Thanks.
I hear something, but don't know if it's just the strain on the engine...but it feels/sounds more like the prop is slipping... sometimes if I slow down and try again it seems to work fine... even if it runs a couple MPH slower.

Used to be outboards had a shear pin... not sure how the current OB function and if there a simple way to test/check for prop slip.... if that's even technically possible.

 

[rrhodes]

Re: Performance - Top End

If your prop is slipping then you would notice your RPMs increase as your speed decreases. I would bet that your RPMs decrease as the strain on the motor increases.

 

[Silvertip]

Re: Performance - Top End

Do you understand what "venting" is. This is slip but it is not a mechanical condition of the prop in some cases. If you have people sitting too far forward, the front of the toon goes down but the stern comes up. It may come up far enough to the point where the prop can't bite the water any longer. When this occurs, have people move quickly to the back. If the sensation stops, you found the issue. If you really feel the prop slipping, there is a rubber bushing between the splined hub and the blade area of the prop. If that rubber cushion breaks loose, the hub can spin inside the outer blade area. This is commonly called a spun hub. To check this, place a mark on the metal part of the hub. directly opposite that mark, place a second mark on the blade area. Now run the engine until the problem occurs. Check to see if the two marks are still lined up. If they are, the hub is obviously not spun. If they aren't, your either need to have the prop re-hubbed or buy a new one.

 

[beermunk]

Re: Performance - Top End

Yeah that's an easy one. You have 6 people in a 22' pontoon with a 40hp. You need a bigger motor.

Tell your wife you need to upgrade to a 150hp for "safety issues." You'll never properly outrun a storm with a 40hp motor.

If she doesn't believe you, lie to her and buy it anyway. Hehehe

 

[5150abf]

Re: Performance - Top End

Define "slipping", does the motor pick up RPM but the boat doesn't go faster?

Next time this happens have people move back on the boat and see if it goes away, as stated you may be lifting the motor out of the water just enough that it is ventilating.

To check for prop slip draw a line across the entire rear of the prop and run the boat, if the line isn't lined up when you are done the prop is spun if it is it is a weight distribution issue.

But as others have said, you are adding 500-700 extra pounds to the boat and nothing kills speed on the water like weight and 40 horse is not alot of power for a boat that big.

 

[boatmor]

Re: Performance - Top End

The bigger boat is not an issue. An even bigger boat will run faster with the same horse power as it will be floating higher in the water.

I had a 28 footer and an 18 footer and changed the motor between them and the 28 ran considerably faster. Any time you start loading a boat you start losing performace. When I had another person aboard the 28 footer I had 56 foot of logs holding that extra weight instead of 36 foot of logs on the 18 footer. Fewer lbs per cubic inch.