Harmonic Vibration

[Scott]

I recently purchased a 1988 Catalina 27 with a Universal M18 with 720hrs, my first diesel inboard, and finally got her out on the water this weekend. Prior to going in the water the shop determined the cutlass bearing was ok, the lasdrip was ok and the 2-blade prop looked fine. I noticed a harmonic vibration practically around 2000 rpm. The vibration decreases as the rpm increases. The motor runs great, there appears to be no knocking, no smoke and pleanty of power My question, Is some vibration normal for this motor? And if not where do I start to fix it? Thank You

 

[Augie Byllott]

You will undoubtedly receive some additional replies but it seems that every boat/engine combination I have come across has an rpm range, sometimes several, at which a noticable vibration appears. As the rpms change it diminishes to the point where it disappears. One or two cylinder diesels seem especially prone to this condition. Mechanics have told me that there is no harm as long as the engine speed is adjusted up or down to eliminate the vibration.

 

[Trevor]

rattling stovetop burners

Hi Scott -You may want to check the engine alignment, but I agree with Augie that it's probably nothing to worry about. I have a similar vibration that rattles the stove top burners and even the companionway ladder at certain RPMs. I make a point to increase or decrease the throttle to avoid that annoying rattle. Probably just a quirk with your particular setup... every boat is unique.Let us know if you find out otherwise.Best,Trevor

 

[Scott]

Thanks

Thank You for the replies.Good to hear that this is normal.