40hp 2stroke 3 cylinder constant squeal and rough/shake

[phisherman]

Hi All,

Long time lurker, many issues solved with your help, this one I can't figure out...

About 3 weeks ago, the motor wasn't peeing forcefully. I dropped the lower unit, rebuilt the water pump (full kit), noticed that the bracket/rubber seal, think it's called a damper seal, between the exhaust and water pump was completely corroded/missing, ordered those parts overnight, cleaned everything thoroughly (exhaust had been getting into water pump area), re-greased and reassembled. The rattle I had been chasing for years was gone and the engine was seemingly running the best it has in 10+ years.

Sat for 2 weeks with my father running it 2-3 times max at *****ing speed. Started rough yesterday, but didn't think much of it at first. Took it for a rip in the ocean and upon getting back into the river, noticed the engine was running very rough/loud, making a constant squeak/squealing noise and rattling/shaking quiet a bit...horrible sound.

Did the internet search. Some say it could be as simple as the the drive shaft bushing/seal...others say its a crank bearing.

To my ears, it sounds like the sound is directly below the flywheel.

2 weeks ago I had this old thing running mint. I know the motor pretty well and do all the routine maintenance, cleaned the carbs twice already this season, use ring free and stabilizer, know how to link/sync (including oil linkage/clearance), all that good stuff.

Today, pulled the boat, warm engine compression test was 105-105-110. Dropped lower unit and ran it on hose clamped to water uptake. Constant squeal was still there so I think the driveshaft bearing can be ruled out.

Uploaded this video of the constant (idle and in gear) squeal attached. Listen to the very end after the engine is killed, the squeal at the very end as the engine slows to stop.

https://www.youtube.com/shorts/17m6xeH_RO8

Not sure what to do next! Very much appreciate any help...

[99yam40]

sounds like the flywheel is rubbing on something.
time to have a look to see if you can tell what is rubbing
pulser coils, charge coil, and lighting coils are close but should not be touching or rubbing

[phisherman]

99yam40, thank you!! Pointed me in the right direction and it ended up being a lose flywheel only. After a lot of concern, was a quick fix and back on water yesterday.

[99yam40]

good to hear it was an easy fix.
did you check the key to make sure it was not damaged?
I guess as long as the timing is in spec,( checked with a timing light) the key should not be damaged enough to need replacing

[phisherman]

I did. Quickly pulled the flywheel to check out underneath. Key looked OK…I though for sure it would be snapped off. No other rubbing. Flywheel magnet has fair amount of corrosion/rust. Is it OK to clean those with fine sand paper?

[99yam40]

yes I would get rid of the rust and corrosion, might put something on it to keep that from growing back

Just a thought I had, do not lube the fit between the flywheel and shaft.
it needs to be clean, dry, and a tight fit.
the key is not supposed to hold anything, it is just to index the flywheel.
the nut tightness and tight fit between the shaft and flywheel is what holds it from slipping

[panasonic]

I have to ask..was the flywheel nut backed off much? Strange for a flywheel to just get loose on it's own...usually it's a bugger to get them off!

Glad to hear that you had no damage.

[phisherman]

grabbed flywheel with both hands and noticed I could rock it back and forth a bit. checked the nut and to my surprise, I could back it off by hand. Didn't even put a socket or wrench on it. Was shocked. Learning now, this is something I should have been checking annually, re-torque etc. Guess I was incorrectly working under the assumption that nut was somewhere in the 80+ ft/lbs range and it would never come loose.

Has me thinking...what other nuts/bolts should I be checking on a regular basis to make sure they haven't rattled loose?

[99yam40]

you say rock it back and forth, but the key should not let it rotate,
maybe you did not rotate it back and forth just up and down.( that even does not sound like the right way to describe it either)

I have never run into a problem with a flywheel nut on any motor backing off.
someone must have taken it loose at some point and did not tighten back up properly.

I know stuff like that happens to us all especially as we get older,
thinking I will tighten it up as soon as I finish doing something else, and then forget to.

A friend drained one of his lower units lube and found out he did not have any at home.
figured he would buy some next time in town.
good thing he had twins to get back to the ramp under his own power on his next trip offshore

[phisherman]

yes, up and down, tiny bit of play, the press fit had not come completely undone, meaning I could not remove the flywheel without using a puller still, but the nut was doing nothing to hold it in place.