I have a 2007 60HP Bigfoot EFI on a 24' suntracker pontoon with 25 to 30 hours on it. Late last year I had 1 or 2 times when my keyswitch would not turn. This year I put my boat in and it started right up with no problems, drove the boat to the dock without issue. When I went to start it up again the key wouldn't turn. I ordered a new keyswitch went to install and the harness was not the same. After many hours and talking to a few boat mechanics they gave me a new keyswitch and told me to solder the wires. No problem, clean connections. Wouldn't start. Found a fuse in the fuse holder assembly number 3 which was blown. There was a 15 amp and I replaced with a 20amp. Nothing. I searched online and found a technician guide and it said if that fuse is blown it is a very good possibility the suppression diode is bad. I replaced and still nothing. I am not getting any power to my trim or gauges. Or the keyswitch from what I can tell.
Also, I should note, this is a pacemaker model so the serial number is throwing all of the techs off.
The key wouldn't turn in the switch so played around with it for awhile. Eventually it broke in half to where I could see 3 little springs and 2 brass plates. I am guessing something at this point shorted out. I bought a new keyswitch with harness and had to solder on because two mercury dealers couldn't find one to fit the original harness. I soldered it on nice and clean installed, nothing. Found fuse blown replaced, nothing. Replaced suppression diode, nothing.
Have you checked the fuse on the motor where the 12v. + cable attaches to the selonid? There should be a small red wire on the same post that should have a fuse in it , and that supplys 12v.+ to the rest of the boat. You might have shorted out that when the switch broke.
OK, I got it working. I believe the problem initially came from the the original keyswitch when it literally broke in two. I think something at that point shorted out. I replaced the number 3 fuse For the main power relay and keyswitch as it was blown. However, there was power coming into that fuse but not going out. It was seated in fine so I took it out and scraped the end of the fuse hoping it was corroded, still nothing. I ended up switching the Number 2 and 3 fuses and it started right back up like nothing was ever wrong. Can't figure out why it took that for it to work. Both fuses metered good.
Anyway, up and running! Thanks for your help guys!