Towards the end of last season this issue happened 3 times. On neither the helm or engine key the motor would turn over. after switching to spare starter same result. The first 2 times after little troubleshooting time it adventually just started working and was fine for a few more trips. The last time the problem occurred I couldn't get it to start so I jumped the starter and motor fired up for for the trip and many trips after that. Where to start on troubleshooting a gremlin that hasn't happened since.
Your looking for a smaller, stand-alone solenoid either in the DC box in the engine room or on the engine. From the starter, follow the yellow wire with red stripe back to this solenoid. Your ships print set should point this out also. This solenoid helps the starter get max current on this wire. It may also keep the engine from starting in gear. Double checking the neutral safety switches could be a plan also. Again, your ships print set may be helpful here also.
