SotallyTober57

I have twin 2005 Merc 200 EFI and I believe I am having an issue with one of the ECUs. It all started last weekend when I was heading out to the sandbar. I was cruising and began losing power from the starboard motor. When I was idling (no wake zone) that same motor (starboard) just shut off. I turned it back on numerous times while en route to my final destination. I did a visual inspection, however, I could not find any issues with the motor.
I decided to let the motor cool for a little while while I was at the sandbar. I had the radio playing the entire time and noticed the battery voltage was reading a hair under 11 volts. I quickly cranked up the motors and only the port motor would turn over. The starboard would crank but not fire. I jumped the batteries (each motor has an independent battery) and finally got the starboard motor to fire, but it was smoking excessively and idling at 2,000 rpm. I almost immediately shut down the motor and decided to idle back to the boat ramp on the one normal functioning motor.
I unknowingly left the jumper cables hooked up as I idled in and by the time I got to the ramp, the other motor began to smoke a little more than usual too. I pulled the boat out of the water, went home, charged the batteries and attempted to start both motors up. The port motor ran fine and the starboard was having the same issue. I pulled all the plugs, cleaned them and reinstalled them. I swapped the ECUs and now the starboard (which has the port ECU) runs fine and the port motor has become problematic.
What could be the cause of the ECU acting up? Did my batteries voltage drop too low and damaged the fragile electroincs? Am I looking at purchasing a new ECU now?

Thanks in advance,
Jason

lakematdude

First you'll want to ensure that your engine is charging correctly.

If you decide to check into the ECU a little further, you could give Simon motorsports ECU repair a call to see if they can be of help.

http://www.simonmotorsports.com/

Good luck.