Loud Squeel above 2000 RPM but only when in gear

[ni7irs]

I have a Mercruiser 7.4 MPI with Bravo 3 prop on a Maxum 2800. All fluid levels are fine, stern drive just serviced with no problems. Above 2000 RPM, engine develops a loud squeel. Squeel continues until 4000 rpm then you cant hear it anymore (whether because of other engine noise or not unsure). I do not get the squeel if i put the engine in neutral and rev up above 2000 rpm, only under load.

Belt was replaced and then tightened. Spun everything with belt off and seemed free, no play noted in alternator. Squeel was there last summer but seems worse now. Any ideas?

If alternator, why doesnt it squeel even in neutral? Why only when engine is in gear?

 

[familyguy]

Re: Loud Squeel above 2000 RPM

Re: Loud Squeel above 2000 RPM

If it only squeals when in gear, it sounds drive related. Doesn't sound like a belt or pulley. When was your drive serviced and what was done?

 

[ni7irs]

Re: Loud Squeel above 2000 RPM

Re: Loud Squeel above 2000 RPM

I just had the stern drive serviced and they said it was in good condition. The sound is definately coming from the engine compartment.

 

[JustJason]

Re: Loud Squeel above 2000 RPM

Re: Loud Squeel above 2000 RPM

Unfortuneately your in front of the boat, we are not.
You have to listen to see if it's a belt squeel or a bearing squeel. There's alot of places noises can come from.

 

[ni7irs]

Re: Loud Squeel above 2000 RPM but only when in gear

Are there certain accessories that wouuld only load when its in gear? The squeel sounds like its coming from the front of the engine, not the rear. My first inclination was to pull the alternator but since I get no squeel in neutral this led me to question the alternator as the problem. I just am trying to rule out suspects before I start yanking an replacing stuff.

 

[JustJason]

Re: Loud Squeel above 2000 RPM but only when in gear

Same thing, squeels come and go. Belts squeel, alternator bearings squeel, water and power steering pumps, they will all make a racket.
If the engine is buried in the boat your going to have to lose the hatch and take the boat out and listen.

If you were paying a shop to do this. They would stick 2 mech's in the boat, 1 driving and 1 listening. That's all you really can do. If you take the replace "this and that" method, your either going to get lucky or get poor.

 

[ni7irs]

Re: Loud Squeel above 2000 RPM but only when in gear

so, it could still be an idler or alternator even though I get no noise in neutral when revved up over 2000 rpm? I want to rule out as many suspects as possible so I can focus on the most likely causes. I am just concerned that it doesnt squeel when in neutral which leads me to think it isnt the alternator because that load is the same no matter if the boat is moving or not. Or am I wrong?

 

[Gary H NC]

Re: Loud Squeel above 2000 RPM but only when in gear

Is this running the one large serpentine belt or V belts?

 

[ni7irs]

Re: Loud Squeel above 2000 RPM but only when in gear

One big belt.

 

[Gary H NC]

Re: Loud Squeel above 2000 RPM but only when in gear

Ok,The serpentine belt.

You do need two people,one in the engine bay listening while the other drives the boat.
A mechanics stethescope will really help.Most auto parts stores sell them pretty cheap.

 

[ni7irs]

Re: Loud Squeel above 2000 RPM but only when in gear

OK. I guess I can't rule out anything based on the fact that it only squeels in gear. Ill get the stethoscope and see. Thanks.

 

[ni7irs]

Re: Loud Squeal above 2000 RPM but only when in gear

Re: Loud Squeal above 2000 RPM but only when in gear

So today, I sprayed some belt dressing and it seems that the amount of noise is less. There still is a loud hissing kind of sound between 2200 and 4000 RPM. I dont know if this is just the way it sounds, but its louder than the engine itself. It sounds like the high pitched whine of a jet engine.

I took a mechanics stethoscope and checked the alternator, the idler, and I didnt hear anything peculiar. I dont know.