[barnacle]

The first thing I would do is replace the water pump in the outdrive. The pump no matter if its a sterndrive, inboard or outboard should be changed every 3 years. What kind of outdrive do you have? You will need special tools to get a MerCruiser apart and back together right. The main tools you will need is the spanner wrench to remove the retainer nut at the u-joints along with the retainer nut at the prop shaft. Even you you do not have a leak I would change the seal at the u-joint shaft. This seal is famous for leaking. Also be sure to check the shaft that this seal rides on.