2003 Yamaha F115TLRB

by Tommie
(Ellabell, Ga. USA)

Have a "weak" spark on cylinders 1&4. have swapped coil positions with same result. Replaced both ignition coils, same thing. Ran YDS software for testing and nothing shows as a fault/warning. Went step by step per Yamaha factory service manual and all test results matched the specs given in the manual. You can start the engine and pull plug wire #1 and no noticeable difference, same if #4 is pulled. If either plug wire # 2 or 3 is pulled the engine will shut down. All ground terminations are clean and tight. There is a termination point for a group of "grounds (red/yel) wires all come together on the port side, that was also checked and was in good shape. The engine starts if you touch the key, the engine hours are 243. any help/direction would be great. TIA