High Pitched Squeel and Voltmeter Over 16

"After reading posts here for

"After reading posts here for quite a while this is my first post.

I have a 1991 Glastron with a 130 hp 4 cylinder Mercruiser. It's out of the water for the season now (it's already cold here in NH); but the following symptoms, at first very infrequently, gradually becoming more frequent, began during the season.

A high pitched squeel eminates from the engine compartment and at the same time the voltmeter is pinned past 16 volts. Backing off the throttle usually stops the squeel at which time the voltmeter pops right back to 14 volts. This initially happened at high rpms, but towards the end of the season it seemed more random, happening at lower rpms as well.

The belt seems to be tight enough - about a 1/2 inch of flex or less. Common consensus amongst fellow boaters is that the alternator is going bad but I figured I'd ask here for any input as well.

Another problem, which I think may be related, is that after running hard (high rpms) for some time, the engine will very infrequently stall at idle then not start again for about an hour or so.

Otherwise this has been an excellent, dependable boat and motor.

Anybody have any ideas as to what may be going on?

Thanks in advance for your help!

David"

"The squeel is most likley the

"The squeel is most likley the alternator. At 16 volts the alt is producing major amps and probably using over 5 hp when doing it. The squeel is probably the belt slipping. The belt may be slightly loose at 1/2" belt flex but the major concern is the alternator voltage.
The problem is in the voltage regulator. Most marine alt systems use a internal regulator. Spend $35-$50 and have it repaired by a pro. That way, it can be inspected for any other hidden problems/suprises
Good Luck"

""after running hard (

""after running hard (high rpms) for some time, the engine will very infrequently stall at idle then not start again for about an hour or so"
Theory only--Less air is moving thru the engine compartment at idle than there is at high RPMs. After the hard run the high alt. voltage, which may have been cooking the electronics and coil, finally caused them to overheat at idle and fail until they cooled off.

After the alternator is fixed see if it no longer stalls. Come back if it stalls again."

"16 volts means regulator in t

"16 volts means regulator in the alternator not working. Replace or , rebuild voltage not to exceed 15 volts"

"Just a note about safety.
Th

"Just a note about safety.
That excessive voltage when it pins your volt meter could easily be double what you are seeing. It could fry any electronics and most important, it could cause your battery to explode. Do not run the boat until it is repaired."

"Thank you all very much for y

"Thank you all very much for your input! I'll probably just replace the whole alternator as I believe it's original to the motor. Sooner or later it will need to be replaced.

Bill, thanks for your word of caution. The boat is out of the water for the season and the alternator will be replaced before it runs again.

Thanks again!

David"

Has anyone heard about 1989 Me

Has anyone heard about 1989 Mercruiser 3.7 litre motors having problems with the voltage regulators catching fire? My mechanic says this was a problem and they stopped making these engines after 1989.