Engine or Prop

[mattjgreen]

27 ' Bayliner w/ 350 engine and Volvo Penta outdrive.<br /><br />Boat will get on plane and run about 30 mph at 3/4 throttle. When I try to go to full throttle the rpm's start to go up and down like the engine is losing power. How do I tell the difference between a prop problem (such as cavitating or venalating) or an ignition or fuel problem.

 

[JB]

Re: Engine or Prop

I/O topic

 

[Mahoney]

Re: Engine or Prop

I would guess you are having and ignition or fuel related problem. If it were ventalation, you would notice the RPMs shoot up dramatically as it ventilated and return to normal as it recovered, not really a feeling of loosing power.<br /><br />Fortunately there are a ton of relatively easy, inexpensive, maintainance solutions to things that could be causing this. However you need to find out which one it is first.

 

[Watercanuck]

Re: Engine or Prop

Pull off the fuel filter, empty it into a bucket and look to see if there is water in the fuel. I'm willing to bet that is your problem. You'd then need your carb cleaned and tank probed.

 

[pvisser]

Re: Engine or Prop

I had a similar issue last year. It turned out to be the water seperator was full of water..

 

[milkyway]

Re: Engine or Prop

I had the same experience last time. In my case, RPM moved up and down the scale and the boat remained "at the same speed" as I put more power. <br /><br />Ran the engine on trailer at 2500 rpm and the engine did not hesitate or showed fluctuation in rpm. <br /><br />Then only then I checked the condition of the hub. Turned out the propeller hub was bad and the propeller was slipping as you put more power to it. <br /><br />You can put the boat on water and run & rev the engine and see how the engine runs. If the engine coughs, then it's not the prop. <br /><br />Or maybe it's just bad gauge.

 

[milkyway]

Re: Engine or Prop

I want to correct myself--- if you put the boat on water and run and see how the engine goes, make sure the prop is removed and the boat secured. Or you can do it on trailer but be sure you have adequate supply water to the impeller.