Boat speeds up

[router343]

I have a 150 hp mercury ob. I was pulling the kids on a tube last weekend at about 15 to 20 mph, the boat will not maintain that speed it either speeds up or slows down on its own, It picked up speed so fast my daughter could not hold on, and almost got hurt. any ideas what i can check to see why it is doing that.

 

[sschefer]

Re: Boat speeds up

There are so many things that can cause this that you'll just have to go with a process of elimination. I would start by checking the throttle control cable to see if is moving freely and in not frayed or bound due to a tight corner or something of that sort.

Next change your fuel filters and check your fuel primer bulb to make sure it is working correctly.

Those are the quick and dirty checks that need to happen first. If it's not there then my immediate suspicion would be a bad plug or internal fuel delivery system that randomly comes to life. But, that's only looking at it from a fuel side. There's the electrical also.

Bottom line, if your not comfortable with all the tests you need to do then take it to a shop before someone gets seriously hurt.

 

[CharlieB]

Re: Boat speeds up

You didn't mention if the boat was on a plane or plowing water.

I suspect that you may be trying to run right on the edge of planing, the boat tries to rise, and overcome the water drag, you drop the throttle just a hair and the boat settles back down, the water starts to further drag the speed down.

I don't normally recommend any of the 'whale-tail' type devises, however in your situation, you want to get the boat up AND keep the speed down, it may be an option.

 

[sschefer]

Re: Boat speeds up

Good point Charlie, I didn't ask for clarification as the whether the boat was speeding up or the engine was speeding up.

 

[router343]

Re: Boat speeds up

i appreciate the replies, Charlie it seems to be doing exactly what you said, and i will check the cables and fuel lines could be combination of both, as for now the boat does not pull any body for any reason, i shut it down after the first incident. There are no problems as long as i am running pretty fast, but i dont figure anybody wants to tube or ski running 40 to 50 mph, lol

 

[QC]

Re: Boat speeds up

Trim Tabs work wonders for this. Very normal though, you just have to be diligent with the throttle . . .