I don't know the specifics, but my friend has a pair of 05 350 mercs. He was out when all of a sudden the port side motor stopped. He was able to make it in in limp mode. The marina said it was a blown 20 amp fuse that is located on the motor by the relays. They put in the new fuse and it fired up.
My thinking is that he has more than just a blown fuse. Why would the fuse blow unless either a shorted wire or the fuel pump is on its why out? Anyone with a thought? Thanks

1.Battery low, Alt. not putting out enough power, either loose belt or bad alt.

2.Had more items on then the alt. could handle.

3.Connection to the fuel pump loose or bad.

Voltage to fuel pump gets low, amps go up. Thus blown fuse.

Boat went out last night and blew the fuse again after about 15 min. Marina will look at it again today, but I'm not confident in their diagnosis most the time!

Check the filter on the suction side of the pump, also check the screen inside the pump inlet, and while you're at it you could take a look at the check ball/anti drain back on your fuel tank outlet if you have access to it. I've seen a couple of those pumps burn out from restrictions on the suction side. Usually once they start to overheat and pop fuses regularly it means the end is near... Good luck, Alex..

Maybe a bad pump?