They are near the back of the engine. Remove all the engine covers including the side panels and lean over the top of the engine. Now look for the plug wires and you'll find the plugs.
They're not a lot of fun to change, but they are doable. Also put your boat and engine in your profile like mine. If I knew what engine you had (200, 210, 240, or 250) I could tell you what plugs to use and the gap.
Aaron:cheers: