I am having a weird noise coming from below deck behind my engine from about 2100-2400rpm. It’s a deep, loud grumbling that’s coming from behind the engine (yanmar 3YM20). The noise is rpm dependent, and it happens in forward, reverse, and neutral. 3000 rpm cruise, I don’t hear it at all. Noise can be heard from 1900-2600, but from 2100-2400 it’s REALLY loud. 90 hours on the engine. Maybe 15 of those hours put on this season. Does anyone have any insight to what this noise might be? I took a video from the front of the engine, which sounds more or less normal. The second video shows the noise coming from the rear. Sounds like it might. E coming from below deck. Thanks!
Strange grumbling noise behind engine
- Thread starter BERK30
- Start date
It sounds a bit like something I had a few years ago, and it turned out to be a cutlass bearing. We limped home for about an hour and maybe I could’ve gone a bit longer, but I got her attended to right away. I meant to add that I dove under the boat and gave the prop shaft a good lateral wiggle. That produced a similar noise, and there was play that should not have been.
Last edited:
I agree with you both. It does sound like it could possibly be bearing related, but it’s likely not the cutlass bearing because the symptoms remain in neutral. The noise coming from the rear is certainly not normal. It has never made this noise before. It’s a bit hard to catch on video, but it’s a low pitch, deep rumble. Somewhat similar to a bad wheel bearing on a car.
Do you have good raw water flow out the exhaust? You might check the condition of your water pump impeller.
An impeller with missing vanes can make a hollow booming sound as more vanes break off.
An impeller with missing vanes can make a hollow booming sound as more vanes break off.
If I heard a grumbling behind the engine, my first reaction would be to immediately locate the admiral.
Water flow out of the exhaust is good. I swapped it out with a new oem one anyways because the old one had unknown years on it. Kept the old one as an emergency spare. Unfortunately, still having the noise and vibration. Thanks for the suggestion
Not sure what you mean by your question. I checked the engine mounts and they visually look ok. Harmonic vibration is a possibility. There is a good amount of vibration associated with the noise. Any advice where to start checking? Visually, the harmonic balancer does not appear to be excessively vibrating. Not sure how to test that
