When I first fire up my starboard motor, the power steering squeals very loudly. If I let it idle it will suddenly stop after a short while as if it instantly fixed itself. If I rev the throttle a bit I can also get it to stop.
Is this just the belt or do I have other problems?
The tension on the belt seems o.k.

CTA

belt

If it's Merc Racing engine, the serpentine belt needs to be set pretty tight, but at idle the pressure in the system should be low if not turning the wheel. If there is a filter, check it or even temporarily remove it. If these things don't help, check for some other type of restriction, possibly a hose that might have separated internally. Hope you find the problem.