Buy a couple hundred incense cones off E-bay. Place them all in a
steel pan on a couple of bricks in the center of the
cabin. Ignite the whole bunch with a
propane torch, exit the
boat. Close up all the hatches and vents and leave it for a few days.
You would not believe the amount of foul
odor that this will cover up in an old car or
boat. I've even done this in old houses.
Choose your scent wisely. I personally prefer patchouli or jasmine for this purpose. Frankincense and myrrh is also a favorite.