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.
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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.
I missed the neutral part. Very sorry but well underway, the prop spins so I wonder if it still could make that noise. In my case, I just don’t remember what it did in neutral.