high-pitched squeal, 50hp 4-stroke

[walleyehed]

Got a 2000 Merc 50hp 4-stroke that on occasion starts to squeal when at idle, then slowly goes away. It sounds like it might be in the mid-section, and was wondering if there is a bearing simular to 2 strokes below the water pump that might be doing this.<br />Any suggestions???<br />I know squat about the 4-strokes, and this is on the State's electro-fishing boat, not my own.<br />Thanks!

 

[hondon]

Re: high-pitched squeal, 50hp 4-stroke

This is something a little new out there , but if that sound is like a whine or somewhat like the wind blowing through your fishing lines ,you may well be expieriencing some harmonic resonnance.Sound about right?

 

[walleyehed]

Re: high-pitched squeal, 50hp 4-stroke

Yea, it does sound somewhat like the wind blowing through monofilament, just slightly louder.........<br />Are you telling me this is normal?????<br /> In the 2 years we've had it, nobody seems to recall this sound before.<br />Thanks

 

[rodbolt]

Re: high-pitched squeal, 50hp 4-stroke

hello<br /> I would not worry about it four strokes dont break.<br /> nahhhh<br /> check the timing belt and tensioner assy. sometimes the belt makes noise while moving past the tensioner.I cannot remember if that motor uses a busing for the lower driveshat that is in the exhaust housing just above the water pump.you may try droppimg the gear case and see if there are any rub marks. dont try to run the motor with the case off as the upper driveshaft splines also drive the oil pump. good luck and keep posting

 

[MajBach]

Re: high-pitched squeal, 50hp 4-stroke

I get this noise all the time on my 90 hp. But never in idle. It's always on a fast plane with the engine trimmed in. Someone moving to the front of the boat is enough to make it go away even.

 

[tarpon]

Re: high-pitched squeal, 50hp 4-stroke

I have a merc 90hp 4 stroke and mine just started the high pitched squeal when at idle.<br /><br />As soon as I increase throttle it goes away.<br /><br />It started right after I installed a new prop. Not sure if that has something to do with this.

 

[dilligafda]

Re: high-pitched squeal, 50hp 4-stroke

Hey guys, try spraying a little WD-40 (or similar product) at the upper driveshaft bushing (near the top where it goes through the adapter plate). I have seen that bushing develop corrosion between it and the aluminum it is fitted into and cause the bushing to ride on the driveshaft and make that noise. <br /><br />Of course to repair the problem means removing the powerhead and replacing the bushing. Definately not a job for the faint of heart! <br /><br />Anyway, good luck and happy boating!!!

 

[kenneths]

Re: high-pitched squeal, 50hp 4-stroke

Thanks for the ideas guys, I'll take a look monday. I'm not a 4-stroke mechanic, but I'm in no means "new" to outboards, so I MIGHT have a chance of getting it back together....I hope.<br /> It's funny, I can teardown a 400,000.00 turbine aircraft engine with no-sweat, and the darn things run when I'm done, but These 4-strokes require a "real" mechanic.....BUT, there are more MOVING parts in the 4-stroke than the turbine, so that explains it........

 

[streadway]

Re: high-pitched squeal, 50hp 4-stroke

i bought a new 9.9 4 stroke this year.it did the same thing the first few times that i ran it.i'm with rodbolt on this one look at the belt.