Get a short section of clear hose, double barbed fittings and hose clamps. On raw water side install clear hose in a couple areas. Then run motor and watch for bubbles, there should be few little
Seeing it on the water means one or more of the cylinders are running rich. Pull the plugs and see which ones have carbon build up. Once those are identified then it can be determined which injectors are at fault
And fuel pressure be 43 psi with vacuum line removed off regulator and no lower...
Could use a serial number of one of the motors
Have you measured the exhaust temp with a IR temp gun?
When was the last time the impellers were changed?
I feel your pain but there is nothing anyone on the forum can do to find the short for you. The Port motor has a short which pops the breaker on Starboard when connected together, got it.
Disconnect the alternator wire (orange) from the ALT and see if same happens. With no helm gauges, measure...
The Main Power Relay (MPR) item 13 is energized by power on the pink wire coming from the key switch. The key switch sends power on the purple wire to the pink. Look to see that you have 12V on the MPR on the Red wire with key OFF and ON. Then check you have 12V on pink wire when key is ON.
You...