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1990 Malibu Euro Mercruiser 5.7 noise

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I recently picked up a 1990 Malibu Euro F3 for what I thought was a very cheap price. This thing was probably not cared for the best and has a good chunk of hours (1480 but the hour meter ticks when the radio is on, who knows how long it has done that).

There seems to be a rattle coming from the front (bow) end of the motor, right around the crank pulley. It doesn't make the noise much until after 1000 RPM and it increases in speed with rpms. My fear is a bearing going bad but I am no expert. I confirmed oil pressure with a mechanical gauge, and it makes about 25psi at hot idle and 50psi cruising at 3000 rpm.

Anyone have any ideas? Video is not the best it's hard to capture the sound. I am going to try to throw some marvel mystery oil in there and see if it helps out any. Any chance it is a worn timing chain making noise?

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Have you changed the impeller? Also check out the water pump bearings. It is not very loud, but slack in the timing chain could be the sound like you said. The oil pressure looks good.

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Could be your raw water pump bearings.

Or, on mine my alternator, the top alt. mount hole keeps getting out of round and the alternator shakes. I had it fixed a few years ago, but it's starting to do it again. It does make a rattling noise.

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  • 4 years later...

Did you ever figure out what it was? I have the same exact boat and it's making the same exact noise. Please tell me it wasn't bad!!

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