i have a 1985 dt85 and lately it have been going and starting fine but sometimes it just dies like its not firing or its run out of feul. i have had it serviced and had all fuel lines replaced right too the fuel tank also had timing and spark plugs replaced then you hit a bump and off it goes like a rocket again we even use this boat to ski behind Oh the only thing not standard it the prop is a 15deg instead of 17. can someone PLEASE HELP