You lift the engine hatch and pour it down on the bottom of the hull. Your bilge is the area (specifically the "floor" area) of the lowest part of your boat where the engine is. Being on a trailer, put bilge cleaner down there. Let it slosh around when cruising, then drain it from the plug. A hose and some rags will clean it up too.
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Former owner of:
1996 Four Winns Horizon 200 5.8L VP
2006 Four Winns Horizon 260 8.1L VP
2007 Sea Ray 290 Sundancer
Current boat
2004 Sea Ray 290 Sun Sport Twin 350 Mags
