I am not real familiar with 4 cycle motors, but I would expect them to share gearcases with 2 cycle OBs. As such, gearcases will normally have a bearing that supports the driveshaft, just under the waterpump, at the top of the gearcase, as well as a bearing where it meets the pinon gear. They should not squeal.
I would recommend you refill the gearoil and see if it still happens. If it still squeals, it is time to drop the gearcase and see if the noise stays with it. You will need to find a way to cool the engine during the test. A barrel of water, under the midsection, plus a sump pump and hose connected to the water tube in the midsection will usually work.
Some motors have flush ports which can work as well.
