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Noise disappears on the water mistery

Old 02-15-2021, 02:13 PM
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Default Noise disappears on the water mistery

What do you think it is?...took it to the marina thinking it was an engine-issue but when engine runs with boat in the water noise disappears.

Lower unit in same position during both tests (up and to one of the sides) :

Noise with boat out of the water (flush kit, up on the lift)

NO noise (boat on water).

Last edited by mgarsal; 02-15-2021 at 02:35 PM.
Old 02-15-2021, 04:07 PM
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How far UP did you have the lower unit?
Old 02-15-2021, 04:40 PM
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All the way up as usual, otherwise it is underwater when on the lift.
Old 02-15-2021, 05:05 PM
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Why run it with the drive up ? Nothing good can come of it.
Old 02-15-2021, 07:14 PM
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OK so the recommendation is to ignore a noise I’ve never heard before?, I never run the boat with the drive up, just happened to do it and I’m not going to just go about waiting for something to potentially break underway and ruin my day.

I plan to just ask them to remove and inspect the gimbal bearing, etc and check again...
Old 02-15-2021, 07:30 PM
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My guess would be the water pump or exhaust manifold. On outboard motors the exhaust mostly exits through propeller (along with some raw water coolant from water pump) so if your outdrive operates similarly then I'd suspect the water pump and/or exhaust manifold. I would highly advise not to run it any more until you get it fully checked out.

Old 02-16-2021, 12:19 AM
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I'd swear it's because the drive is all the way UP,
BUT
you say it was all the way UP in the second video also?
Did you go outside and listen when it was in the water?
Old 02-16-2021, 12:47 AM
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I heard a tick off load - do you have a shear pin loose
Old 02-16-2021, 03:19 AM
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Are we talking about the belt squeak?
Bear in mind that with flush kit installed you have pressurized water at the seawater pump, changing the dynamics of the belt tensioning system. Hence the belt squeak.

As far as not hearing it before, a new unstretched belt probably makes it all go away.
Old 02-16-2021, 07:52 AM
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Originally Posted by Baldilox01 View Post
Are we talking about the belt squeak?
Bear in mind that with flush kit installed you have pressurized water at the seawater pump, changing the dynamics of the belt tensioning system. Hence the belt squeak.

As far as not hearing it before, a new unstretched belt probably makes it all go away.
A new belt was installed about 10 hours prior, but will definitively check on this. I initially thought the belt as a possibility but my mechanic said he checked with his stethoscope and suspected something internal to the engine.
Old 02-16-2021, 07:55 AM
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Will ask the marina to check on this!
Old 02-16-2021, 08:12 AM
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I have the same engine and had the same noise. At idle you could hear it, but when under way it would go away. I had the mechanic replace the idler and tensioner pulleys and the noise went away. He said it was the bearings in the bearings going bad in one of the idler pulleys.

Hope that helps

Last edited by fatcat14; 02-16-2021 at 08:29 AM.
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Old 02-16-2021, 11:36 AM
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Thanks for the comment, and will check on this....Both idler, tensioner pulleys and belt were replaced less than 10 engine hours ago. These are brand new original parts...but you never know I might have gotten a defective one.
Old 02-16-2021, 02:32 PM
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Make sure the belt wasn’t replaced with one slightly larger........ See if you can get the actual belt number called for by mercruiser and cross-reference what was put in. 🤙🏻
Old 02-23-2021, 02:44 AM
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My money is on a lifter that loosens up as the engine warms up.

check out 2:14.


a good way to eliminate options is to spray some water on belt and try to start eliminating your potential options. Belt squeak is a big one (get a gator back these work great), pulleys going bad or just not aligned (bad gets replaced, not aligned can drive you nuts). Valve lifters getting stuck tell you to run some cleaner through it and may need to pull top end apart sooner than later. Not a terrible job but make sure you know what you’re doing.
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Old 02-23-2021, 06:11 AM
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Is it my imagination or is the engine running at higher rpm on the lift than is does in the water?

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