[Bob B]

A fishing bud of mine has an intermitent problem with his new 311 Nitro with a two cycle 225 Mercury. Usually at the beginning of a trip his boat gets out of the hole fine. As the day progresses it gets increasingly harder to get the boat out of the hole and on plane.

On a normal trip he can ease the throttle forward and the boat jumps up and on plane easily. After the first or second time getting up on plane it gets harder and harder to to get up on plane. Eventually, with the throttle wide open it the engine sounds like its bogging down and there is not enough RPMs to get the boat on plane.

He has had two mechanics look at it several times and it runs fine in the shop. The last mechanic finally suggested that it may be the prop. Im not sure about that. I would like to help him, maybe someone out there has a clue to what might be happening. Any suggestions appreiciated. Thanks
Bob B

 

[Bob H.]

If the prop was spun there'd be high rpm's, the engine wouldn't bog down. Could be a heat soak problem in the electronic engine controls since the problem seems to happen after the engine has run for while. Vapor lock in the fuel line as the air warms would also be a consideration.

 

[Bob B]

Thanks for the reply Bob.
Like you, Ive pretty much ruled out the prop as the problem. I thought about it starving for fuel but when the problem occurs Ive squeezed the primer bulb and it is always hard so I know fuel is at least getting to the engine. And when it finally gets on plane it runs great. I dont know a thing about engine electronics, that could be it.
If you think of anything else I hope you will post.
Bob B

 

[Bob H.]

I don't have any idea's since I'm not familiar with the 225. The symptoms indicate a low speed air/fuel circuit problem, whether it's carb or electronically controlled injection. If the engine has variable timing that could be a problem also but air/fuel ratio is the more likely. Although expensive, a spare controller comes in handy for troubleshooting intermittent problems - but my spare won't work with a 225. If the problem only crops up when the engine is warm I would take a good look at the electronics.

 

[Little J16]

Heres a dumb question. Did you put the plug in?

 

[Bob B]

J16,
They say there is no dumb question but I was about to put your remarks in the "dumb" category when I realized what you were getting at. The plug was in and there was no water in the bilge. I forgot to mention that the motor is fuel injected. Thanks for the reply. Any body else?
Bob B

 

[poc]

Sounds like an overheat revlimitter problem..or you are dropping a coil when the powerhead gets warm. A cracked coil will fail when the motor gets hot.