Mercruiser 3.0 making a screeching noise

[M2theB]

I think its alt related as I have had battery issues but I am not sure. The screeching noise comes and goes.
when I start the boat if I give it a bit of throttle while in neutral I get the noise but does go away. When trimming up/down I sometimes get the noise. When steering I sometimes get the noise. Can quite tell where it's coming from but it is loud by my definition.
I took videos of the slack in the belts while turned off and there appears to be a lot. How snug should my belts be? Is this the first place to start before replacing expensive parts?

 

[Alumarine]

Does sound like your belts are loose or belts and/or pulley's are glazed.
Here's specs for a 1978-1984 3.0
Alternator belt should have 1/2" of deflection.
Power steering belt should have 1/4" of deflection.

Here's some info.
https://www.seiffertindustrial.com/belt-tension-methods-instructions/

 

[M2theB]

I am going to be heading out for a ride today. I will take a video of the noise as I am not sure what's going on...

 

[wahlejim]

Same thing happened to me. Alternator squealed when batteries needed to be charged. Would happen on startup when alternator was recharging the battery and any time a heavy electrical load was hitting the battery (ie trim pump). Had a local shop refurbish the alternator, squealing stopped.

 

[M2theB]

I had my wife drive while I listened and I can hear the squeal coming from the alt side. Belts are about 3 seasons old and the alt appears to be original. Will pull it and take it in to have it checked. Fingers crossed that's all it is

 

[Rick Stephens]

Make it easy on yourself. Take 5 minutes and pull the belts and run it on muffs for a couple minutes. No noise, you know what the issue was. Alternatively, take a can of belt dressing with you on your lake run and give the belts a squirt.

 

[Bt Doctur]

As belts wear they sink lower and lower in the pully, then they slip no mater how tight you make them