Can't find the spec for the gap for the 350 mag horizon inboard. It has the platinum NGK plugs. Is it .045 like the rest of the lineup? It's a 1999+ (boat is 2002) Serial #'s start OL3......
Also there is normaly a sticker on top of the engine some place like the flame arrester, ect, with the engine specs on it, It should tell you what the gap is, As long as everything is still stock.