Yanmar 55hp vibration

[sailon46]

I am somewhat worried. Bought a boat Bene 46 Sense 2014, about two months ago. Whenever the engine revs 1500-2000 rpm no gear engaged, or emgaged for that matter she produces a very noticeable harmonic vibration. Low rpm and anything above 2000 no issue. I am worried that if not taken care off it may precipitate who knows what.

[Sailmonkey]

Have you checked the alignment? Or is this a sail drive?

——edit, noticed it occurs with out gear engaged———

How are the mounts? Are they sagging?

How many hours? May be time to service the injectors, might not be fueling all cylinders the same.

[sailon46]

Sailonmonkey, Thank you for the quick reply, I will look into your suggestions for the motor mounts maybe loose, although motor has less than 300 hours on it. I will also look into the injectors.
Ernie

[tkeithlu]

It sounds to me more like, as you suggested in your first post, a simple harmonic vibration. It does not sound from your description that it is going to tear the boat apart, but it could still be annoying. I suggest that you try this: Start the engine and bring it into the harmonic range. Listen and feel around until you find the part that is vibrating - it could be anything from the throttle cable to a part of the boat's frame. When you find it, change its harmonic frequency by tightly attaching anything from a weight to a piece of additional wood. Just get it changed enough that its harmonic frequency is not in the range of your engine RPMs.

Automotive engineers spend a lot of time removing harmonics that correspond to expected automobile speeds. And the history? Tacoma Narrows Bridge and the BOAC Comet airliner. Happy hunting.

[Sailmonkey]

Originally Posted by sailon46

Sailonmonkey, Thank you for the quick reply, I will look into your suggestions for the motor mounts maybe loose, although motor has less than 300 hours on it. I will also look into the injectors.

Ernie

With 300 hours I would rule out mounts and injectors.

Our boat has a harmonic that will shake the stove apart around 1400-1500 rpm. Which is ok as we motor either 1200 or 2200 rpm.

[bombardero]

Originally Posted by sailon46

I am somewhat worried. Bought a boat Bene 46 Sense 2014, about two months ago. Whenever the engine revs 1500-2000 rpm no gear engaged, or emgaged for that matter she produces a very noticeable harmonic vibration. Low rpm and anything above 2000 no issue. I am worried that if not taken care off it may precipitate who knows what.

It would be advisable to check the fixings of the motor to its bench and ensure the good condition of the Silent-blocks.