Causing problems for myself - need help on 15 amp fuse blowing.

[breeves2245]

Posted this in the electrical forum as well. Mercury 50 hp year 2017, so basically new. Can't believe I pulled this bone head play, but I was switching out batteries and got the +/- backwards. Of course when I go to test crank I got nothing. Check the fuses and two are blown. The main circuit 25 amp and relay/accessories 15 amp. Ok, figured if that is the worst of it, I'm good. Just got back with the new fuses, then double checked I got the battery cables correct. Start to crank it and the 15 amp blows but not the 25 amp. Tried again after replacing the 15 amp, same thing. Googled it up, but did not find much to help. What's next? No corrosion, garage kept and everything is show room condition.

[breeves2245]

Called the dealer and a tech walked me through it. There is a protective diode wiring harness that has a ground wire and another wire connecting to the power. We by passed that wiring harness direct to the incoming wire and it worked, engine turned over. Just need to replace that harness. Whew, worried I had fried something expensive!

[JOE54]

must be 4 stroke ?????? might wanna check in that section