A friend of mine (Fred) was recently inspecting a Ben 352. I own a 352 and Fred has spent alot of time sailing around in it. Fred would like to buy a 352 that's why he was looking at it. During the inspection he asked the seller to start up the engine, which he did. Fred said the engine started okay, but made a hell of noise - strong tapping sounds and knocking. He lchecked over the engine while it was operating and could not see any loose parts or anything. The engine type (Yanmar 3GM30) and insulation is that same as my boat. The owner said the engine always sounded like that. According to Fred, my engine purrs like a kitten in comparison. Now if Fred moves forward he will get a mechanic to inspect the engine in detail. Although, Fred and I were comparing notes, and it would seem that there is a wide range of sound levels that come out of marine disels. Why is that and would a good tune up reduce the noise level? Any ideas other there.
Yanmar Noise
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Ahhh , so many parts and so little time.. could be external noise, bad alignment making prop shaft smack into log at resonant frequencies (my 34 used to do that).. bad motor mount allowing engine to hit the supports and the above as well.. badly unbalanced prop from electrolysis.. bent shaft from a bad boatyard lift , worn out Cutless.. Those are the relatively cheap ones.. Then there are the internal engine ones like bad bearings or a loose piston .. many more.. A good mechanic should be able to determine where and what..
I have the same situation on my 2008 Catalina 320 with the 3YM30 Yanmar. I've had the shaft aligned, the mounts checked and it has not solved the problem. Mine begins to clatter when in forward at 2000 rpms and seems to smooth out around 3100 rpms. Marina believes that I may have an unbalanced prop. The noise doesn't seem to affect performance and I will live with it until my next haulout in a couple of years.
If he had the compartment open and was looking at the engine it will of course seem loud. I was amazed when I fired up my diesel for the first time. It sounded like two railroad workers driving a spike! I'd chalk this one up to his inexperience if he hasn't owned a boat with a diesel before.
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