Is your motor fuel injected or does it have carbs?doese spark seem ok or is it ok?It should be a blue spark,at autozone you can buy a spark tester for a few bucks!!Should jump 7/16 of inch,if not it will never run rite!!once you know for shure spark is good and problem still there then start checking fuel system,if you have primer on ignition push it and if boat wants to run with primer engaged.if you have carbs look at the bottom of each one there should be a screw on each side of fuel bowl,take screw out of both sides and run a wire threw it,this is your main jets,if you clean with wire and runs better then rebuild carbs!!