2003 x-2 mcx having check engine light
Having lots of trouble with my boat at the start of the season. Had to take it in cause the check engine light comes on then the engine bogs down slightly. Goes away and runs smooth the repeats. Had a code of 51,81 in the computer. The shop changed spark plugs, plug wires and changed the computer. It's the mcx 350 engine. I picked up the boat and went to the lake it immediately did the same thing. Check engine multiple times and bogging down. Runs smooth then rough at any rpm. Took it back to the shop and said it was the main harness loose to the engine...picked it up today then took it out again. Same issue. Idle ran up and down between 600-700 up and down. Check engine coming on from time to time. Throttled down and same thing. Very frustrated expensive canoe owner! Help please?