About a month ago I bought a boat with a 88 evinrude xp 150. First week I had the boat it ran fine but I haven't been able to use it since. Sometimes when it's idling its almost like its loping. Sounds like it's fightin to stay alive but it will idke forever. If you bump it in gear it's fine sometimes but sometimes it's like it chokes out and dies. When you give it throttle it acts like it wants to go until you hit half to three quarter throttle it's like it loses the power that was building up and if you put it full throttle the motor doesn't rev high or anything it just barely goes. We have cleaned carbs changed a coil redone fuel system such as hoses and new spark plugs. Does anyone have any suggestions. Was thinkin maybe timing off? I don't know what else to try. Thanks for the help in advance