Performance Limitation Underway

[Alan Eland]

A problem recently surfaced while motoring with my Yanmar. While underway the engine will only rev to about 2,100 RPM. Any attempt to go higher simply bogs down the engine (keeps it at 2,100 but sounds as if it met a governor). One attempt produced a lot of excessive smoke from the exhaust. When the engine is not in gear it revs up past 3,000 RPM and sounds great. My initial thought was that something may be tangled in the prop or shaft restricting movement beyond a certain speed. Any thoughts?Thank you.Alan Eland

 

[Gordon Torresen]

Reduced shaft speed

Your first thought is the most likely and the easiest to check. Its nice weather for swimming anyway. There are lots of other possibilities but check that the shaft rotates freely first. If that is not the answer, come on back. Let us know what year and model the engine is and we will start the thinking process.

 

[Alan Eland]

Thanks Gordon

Gordon,Thanks for the quick response. I probably won't be able to go swimming until next weekend . . . stay tuned and I'll let you know how that goes. Quick (probably silly) quetion. How can I check that the shaft rotates freely? If the boat is in nuetral should the shaft rotate freely? Can this only be checked under the water?Thanks again for the quick response.Alan Eland

 

[Ron Dague]

My 2 cents worth

Rotated mine yesterday. So yes, by putting the transmission in neutral, I was able to very easily turn the shaft, one hand. I could hear and feel the blades on my folding prop fall open and close, due to gravity, as they turned.

 

[steven f.]

barnacle's

Had a similar problem several years ago (without the black smoke). I went for a nice refreshing dip and expected to find a crab trap line tangled in my prop only to find a football sized hunk of barnacles around the prop. The prop was nearly one solid hunk of rock. Cleaned it off and away we went. Yet another lesson learned the hard way.

 

[Gordon Torresen]

Payment earned

Ron Dague's two cents worth is accurate. You might forward payment to him to help defray the cost of the starter he needs.