Had problem with Suzuki ,would start hard but once started would run over 3 mph fine. Changed plugs and nothing changed, so I pulled plugs to look at and found 1 cyl. Was not Evan getting fuel. Pulled carbs, cleaned and ran new line. Thing not only starts easier and idles down but I gained a ton of power. Would change plugs, run it for a little bit and look at them. That would be my first step. Will tell you alot. If not good at reading them ,mark plugs for each cyl. And take them to marina.