Since water is drawn in by the inlet holes in the outdrive, is there a shutoff somewhere on the engine that can be closed to do maintenance?? I have twin merc 8.1 with bravo3 attached, usually haul the boat out in the winter and attach muffs to winterize and place coolant in the motor. This year, the boat is staying in the water, and I need to figure out how to winterize this year. Everyone at this new marina has bigger inboards so they have a seacock that can be shut on/off to prevent water to get into the block, how does this work for sterndrives? I've been looking all around the motor and I don't see one for it. I have looked through the manual and it says to empty with the 3 blue drain plugs and use the manual air pump to open the drain valves. When I open one of the blue plugs [starboard top plug] I get a lot of water coming out and it seems like its just water from the outside and not just the block....so much water it filled my bilge area fairly quick within a few mins.