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Rattly new engine


larryjc

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Went for  a spin in my new boat the other day (well new to me).  It has a Beta 38 with only 1600 hours on the clock and runs very sweetly, except below 1000 rpm when there is a horrible rattle which sounds like something knocking in sympathy with the engine rpm. Pretty sure its not internal to the engine and its almost certainly not the drive plate as it occurs in neutral. I've had a drive plate go before and it doesn't sound like one.  I suspect engine mounts.  I can't feel any play in them but the manual says thats its possible that the stud that goes through the rubber mount could be screwed in too far and can hit the bearer.  However, I spoke to Beta and they say that the 38 mounts don't have that type of mounting.  Won't be back at the boat for a fortnight so wondered if anyone else has had this problem and solved it????

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there have been similar reports on here recently. My 50HP Beta (both are Kubota engines) also rattles when cold and at tickover - as it did with my previous one.

Sooo - mebe it's "a design feature" rather than a fault? 

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Yes - going to try the long screwdriver trick and also as the noise changes when I stand on the engine, I'll try pushing one way or the other to see if that makes a difference.

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I had a nasty rattle once.  Took it in to a boatyard where the engineer kindly pointed out that a lump of steel, used as ballast in the bilge, was knocking against the engine bearer.   He didn't charge me and I've learnt a lot about boats since!

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4 hours ago, larryjc said:

Went for  a spin in my new boat the other day (well new to me).  It has a Beta 38 with only 1600 hours on the clock and runs very sweetly, except below 1000 rpm when there is a horrible rattle which sounds like something knocking in sympathy with the engine rpm. Pretty sure its not internal to the engine and its almost certainly not the drive plate as it occurs in neutral. I've had a drive plate go before and it doesn't sound like one.  I suspect engine mounts.  I can't feel any play in them but the manual says thats its possible that the stud that goes through the rubber mount could be screwed in too far and can hit the bearer.  However, I spoke to Beta and they say that the 38 mounts don't have that type of mounting.  Won't be back at the boat for a fortnight so wondered if anyone else has had this problem and solved it????

Could be the air filter box.

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55 minutes ago, mrsmelly said:

Could be the air filter box.

That reminds me - After I had serviced the engine (Beta 43) there was a metallic ping sound that was rpm related.  The air intake horn on the air filter box was almost touching the sump oil extractor extractor pump handle and was tapping against it with engine vibration.

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12 hours ago, Tony Brooks said:

Are the bolts holding the mounts to the beds tight?

Yes they all seem tight including the lock nuts under the engine mounts which is why I was considering that the studs themselves might have been screwed in too far and were protruding below the mount and touching the bearer beams.  As I said, the manual says this is a possibility yet Beta themselves say that the mounts they use on the 38 don't allow it.  When I get back and having purchased a 24 mm spanner I can check it all.   

I don't think its the air filter box although I'll check because the sound is very 'solid' and the box is thin sheet steel. Oh and on the 38 its the opposite side to the sump pump.

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