Resonance

[Vronsky]

My boat resonates at certain RPM levels of my DF115A, creating a very loud noise.
Do you know of any solutions to lower this resonance/vibration ??

THANKS,
V.

[Murray]

Something is loose. Is the vibration coming from the boat itself or the engine?

[Vronsky]

Thanks. Motor is the source of the vibration.
I will measure the rpm & speed ranges where this resonance occurs this weekend.
It does happen between hull speed and planing speed.

[Murray]

I’m assuming you have had the engine cowl off and have checked all fasteners for tightness?

[Moonlighter]

This kind of resonance is almost always due to loose fittings on the hull or similar things.

I get a similar resonance on my boat at idle speed and I know exactly what causes it - a fold up aluminium bench seat that touches the transom. I can stop it simply by pushing against it with my hand.

You could try to isolate the resonance in your boat by adopting a similar approach - applying pressure to various components when it’s happening until you find one part that responds, and then figure out exactly where the parts are touching and how to stop the vibration.

You can also get transom pads that fit between the engine bracket and the hull to help reduce vibration transfer.