switch or ground electrical question?

[txj33p]

Was out this morning with company watching the start of a boat race and just creeping along with enough headway to maintain steering. The garmin unit wouldn't power up at the dock so I left it off for a couple of hours then on impulse tried it again and it powered right up. About 45 min. later I turn back for the dock and start to throttle up when the alarm goes off on the starboard engine followed by the port one. Shut them both down sat for bit and tried starting them up starboard started and ran at idle, peeing a decent stream and the gauge showed green. Started port side and it ran at idle, good stream and gauge green.

Started to advance throttle and boom both alarms go but still stream and green on the temp gauge. By now guests were a little concerned. Shut down the both engines and then went to restart. Switched on port side and got alarm immediately, shut it off. turned switch on starboard, three beeps and started. started limping home at low rpms. tried different things and seemed like every time I tried the port side it would act up and trigger alarms on both. The port switch also activates the panel with the fuses so it has the majority of possible connection issue I think.

By the way these area pair of 97 Yamaha 150's.

So any thoughts on what may be the issue? I was wondering if it might be a ground issue, looked into the back of the dash panel and it is a scary nest of wiring indeed. need to fix this before I can go out again. Thanks in advance for you help.

So any thoughts