1990 model 2 stroke - this is the third impeller I replaced over the years on this motor. Three cogs were off and water flow was erratic. My question is, should I use gasket sealant on the gasket between the lower pump casing and the gearbox? Automotive type stuff ok? Want to keep the water out of the oil in the gearcase. I did not do this last time and had water in the gearcase oil when I drained it. Also is the new four stroke Tohatsu/Nissan/Merc/Mariner 6 hp a good choice for my lake bound Hunter 23? Are these quiet? I have a Tohatsu dealer a couple miles away and a mechanic that can service it.