So I had a very similar issue....fuse keeps blowing every time I try to start the engine........
I tried couple different ways to solve my issue and the most subtle solution was right in front of eyes the entire time.
Method 1.
Get a circuit tester, the old school one with the light.
connect to ground or negative post on battery and turn the ignition and start checking which connections got power, just process of elimination, and if all that checks out OK, then I would just assume you have a short to ground somewhere....
Method 2.
You would need to find the short to ground by tracing the wires and yes it can be very time consuming...
Or you can do what I did, which I do NOT recommend......just get a nice thick solid wire something around 10-12 gauge...or maybe even a screwdriver and just jam it in the fuse holder(the fuse on the engine that keeps blowing) and turn the key and see where the wires are getting hot or even starting to burn the insulation (tell tale sign is SMOKE).
In my case......... I had a short to ground and I located it after trying different forms of elimination.
Turns out my buddy that I go fishing with, and I left the boat on his driveway for a few days and he installed 2 cup holders on the each side of the boat, which was a very nice gesture.
So.... coincidentally the ignition wires were running along behind the panel he screwed the screws for the cup holder and one of the screws screwed right through the entire wiring harness and through some of the wires(purple wire was one of them). It was a simple fix, just cutting and stripping wires and using heat shrink connectors. And also to never ever let anyone install harmless accessories on my boat.
