Mercury outboard making strange noise

Guys

The last few times out my 40 hp Mercury outboard (2-stroke, 2004 model year) has made sort of a squealing or screeching noise at idle or low speed. Not overly loud. But sort of a noticeable squeaking. Closest sound I can describe it to is like a bearing starting to go out. Motor runs fine etc., but just wondering if any of you had experienced anything like this and what your thoughts were.

Thanks.

I had a Merc 60 that did this for years. Never found out what it was, but it never was an issue.

The first thing I would do that’s easy is check the gearlube. If it’s low or burnt or if there’s a lot of water in it you might be loosing your pinion bearing in the gearcase. The other thing to do is to find out if it’s the engine or gearcase side that’s squeeling. When an engines running in the water with a gearcase problem it’s hard to tell because the noise comes right up the midsection. So sometimes you have to pull the gearcase off and run the engine to see if it makes the noise with the case off. If it’s the powerhead then your probably looking at a bearing going out, but that is not nearly as common as a gearcase bearing going out.

I’ve heard of this happening with some Yamaha’s. The attached pic is from another website showing the bushing that squeaks. This is the description they included
“Better pic of yamaha “belt squeal” culprit. Pic of yamaha bushing that causes the “belt squeal”. The tip of the screw driver points right at it. A splash of water up there will take care of the noise for a few minutes…A squirt of silicone spray will take care of it for a few weeks…The “correct” fix is to pull the shaft and bushing and grease the pizz out of it.

My understanding from talks with yamaha techs…this squeal is a annoyance but not a part that will fail.”

Some Mercury and Yamaha motors shared quite a few parts so it’s worth spraying some lube on this area and seeing what happens.

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“Belt squeal” is exactly how I used to describe the noise mine made.

Interesting. Thanks for the info, guys! I’ll do some more research/poking around.

It would really help if you could narrow down where the noise is coming from. Under the cowling/engine area, lower unit, etc.

I know this is a little difficult to pinpoint when running the outboard on the muffs. It might be better to have it in the water, take the cowling off, and find out if it’s under the cowling first.

There are two many could-be options to list without narrowing it down to a “where” first.

Grouse