Thank you to all who took the time to reply with your suggestions... I ended up going up there today to look at it... The larger yellow wire is ground to the motor and the other yellow goes to a bus bar full of small yellow wires, surely another ground... And the small black I didn't trace...
There is no main battery switch., But trim wouldn't work if there was one and it was off... I think yourself and briangcc are right, one of the cables (wild guess the one in the tubing/conduit) should be positive... But we aren't going to guess, either I will go up there at some point and...
The boat has no power to gauges, blower, bilge, horn, lights, starter, etc. But the trim works.
Mercruiser 3.0 stern drive engine/. Boat is the sport model with the sundeck/sunbed on the bacl with the engine under it.
Backstory...
First time trying to start the boat since winter.
My...
