Squeal from belt area/alternator

[Jono]

I've got a squeal coming from the area around the alternator, but I can't pinpoint it. I don't know if its a bearing or a belt. Its been happening for a while and it getting more frequent/consistent. It only occurs when the boat is put into gear and the RPM's climb off of idle. It will always disappear after a few seconds. It also happens on startup. And again, disappears after a few seconds. During the startup ephisodes, the squeal doesn't seem to be as intense.
The belts appear to be OK, but appearances can be deceiving. I have no idea which dart to throw after replacing a belt.

1996 Super Sport

[jasper]

If the squeal only happens during acceleration of the rpms, it is most likely a belt that needs to be tightened. Check for belt dust in the plane the belt operates in. If you don't find any, it could still be the belt. Check your belts for cracks while you're at it and replace if you find any.