Looking for HELP I have a 25' Pontoon Boat with a 3.0 I/O and a Alpha one outdrive

[John60]

I have a 25' Pontoon Boat with a 3.0 I/O and a Alpha one outdrive
When running at 1800 RPM's unit runs fine but under load at 2300 RPM's feels like it just spins and does wait to go faster.
Any input is appreciated.

 

[tpenfield]

:welcome:

Can you elaborate on the issue that you are experiencing at the 2300 RPM range?

Thanks.

 

[HotTommy]

It would be helpful to know more. For example, is this a new problem? If so how did it run before? .... I know nothing about your drive system, but I can imagine it might be a problem with engine power, slippage in the drive or a problem with the prop. We'll need more to help. ..... BTW, there are other forums here on iboats.com that deal with specific engine issues by brand. Just because its mounted in a pontoon boat doesn't mean its a pontoon related problem.

 

[ahicks]

It could be a spun prop. Doesn't happen frequently, but on occasion the rubber center of the prop delaminates from the prop itself. They'll often act like you describe. Fine on idle, but with more power added, at some point they just let go.

If this just started with a prop change, it could be the design of the new prop, or the wrong size new prop.

There could be something going on in the water just ahead of the prop, like a tree branch or something, disrupting the water flow to the prop.

Excessive "up trim" would do it.

Excessive weight forward weight distribution could do that.

Beyond that, it would be interesting to know for sure if it's been an issue since the boat was new, as it could be a design or outdrive installation problem.

Pictures of the boat while out of the water, taken to allow comparison of lower unit height to bottom of pontoons may help there.

 

[John60]

This is a new problem we got this boat last year used it's a 2001 Sun tracker Pontoon the boat ran fine last year. The boat starts up fine and trim works. When I went out yesterday it was our 1st time out this year. The trim was down and we had been out for about 30 Mins. in the river at 10 MPH when we got to the lake and I started to go faster is when problem stared. It sounds like the Engine is work but power is no getting to the peop
we both were seating in the back half of the boat.
We just got into boating so I have little experience with boat motors but I have mechanical experience.

 

[HotTommy]

Good start at providing better information. What is your usual peak RPM? Did you stop at 2300 RPM because it wasn't working right or was that all you could get with full throttle? We're following ahicks' questions to determine if the engine is not running properly or if the propeller is not doing its job. .. BTW, how hard would it be to run the boat again to do some testing?

One way to test for propeller slip is to put indelible marks on the prop and the hub, then run the boat until the symptom appears. If the marks are no longer lined up, the prop is slipping on its hub.

 

[John60]

The engine appears to be running fine I can get more RPMs but stopped as not to hurt the engine. I will mark the prop and hub to see if it's moving. if this is not moving what other things should I look for? I will be taken the boat out later today or tomorrow to check the prop

 

[Cat nip]

Sometimes all it takes is for a small stick or some other floating debris to get coughed in the right spot on the prop or transom to cause the prop to suck air. It happens a few times a season to me when I am on the river in high flood waters. Usually all you need to do is toss the salad, put it in reverse and throttle up a few seconds and then be on your way again.