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Discussion Starter · #1 ·
Hi Sailors, I've got a Yanmar 3YM30 with 650 hours and I am getting a rattle at idle and up to about 1400 RPMs. It happens in neutral mainly and goes away if I increase idle in neutral or in gear. I can still shift smoothly into gear and there's no abrupt knock when I do it.

I am trying to figure out if my Dampner plate is going bad or if it's just a mount. At 1000 RPMs in neutral, the click, click, rattle noise does sound like it's stemming from the bell housing, and when at the dock you can hear it outside the boat on both port and starboard sides equally.

I am hoping it's not the dampner as I just relaunched after a big haul out and paint. Plus hoping not to have to pull shaft and trans to switch this out now - probably can't be done in the water too easily as max prop will have to be removed.

Does anyone have experience with how soon you should change the flex plate in the bell housing when you start getting some rattle - if I continue to use occasionally and it goes, will it break the transmission, driveshaft and/or bellhousing completely.

Seems a little early (650hours) for the plate to be failing. Any experience with this greatly appreciated.
 

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I've had them fail that soon. I think idling in neutral is tough on their life, maybe? What you describe hearing is very likely just that. Starts with a little ding sound...get worse. Bummer your engine is tough to remove....but you really have to haul and remove the prop? Cannot you just undo the four coupling bolts, the four mount studs, and a few other little things (heh!) and lift the whole mess out?

I have run for some time with the worn plate. But no noisy idling, just powered up quiet motoring. The rubber bits go first, then the springs start eating into the disks, falling apart, the whole thing destroys itself.
 

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Discussion Starter · #3 ·
Thanks Aloof! I am going to see if it can be done in water first. Problem is I've got a v-drive and cramped working conditions on the Pearson 323. With a skeg hung rudder I'd estimate I've got about 6-8 inches before prop hits skeg to work with.

So it may be too tricky to disconnect coupling and slide shaft back enough. Would hope pulling the engine wouldn't be necessary for such a semi-routine part. Will go ahead and do the engine mounts while I am at it. I figure I could run a bit like this, I never leave it in idle (800 RPMs) as the Yanmars just shake so much, so I am always idling at 1200, sounds better that way! :)

So, I am guessing once it's too hard to shift into gear, and you get a loud abrupt knock when doing it, that would be the last straw and time to replace???
 

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I don't think it affects shifting much. It does probably wear out the transmission if not running smooth and quiet.

Yeah, the V-drive is a problem with the shaft. I remember that from the previous boat. I'd remove the prop and shaft in the water, or have a diver do it. I'm okay with the resulting leaky hole, if necessary, but can understand some people are not so brave/foolish...
 
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