Lot of folks with Gemini's set their honda gen's on the back step and cover it with a Tupperware garbage can. They have one side cut out for air that faces aft so the noise goes that way. Using pink foam slabs (from home depot) as a underlayer keeps it from vibrating the deck which is a major component of the noise. Stores in the garbage can in a aft lazerette when not in use. Your boat will of course be configured differently.
Another good method is to hoist it with the main halyard so it's 10 feet off deck, then pull it forward so it's suspended over the foredeck - watching that it's not upside down of course by using a outboard sling attached to the halyard.
I've not tried either of these, just passing on stories and descriptions of photo's.