15a fuse keeps blowing when motor turns on

Hello! I have a 2015 Bayliner 170 BR. It's in excellent condition and gets serviced every season.

All of a sudden, the 15a fuse keeps blowing AFTER turning the motor on. I can get the boat running, but blows the fuse in the process... which means I can't get it started again without putting a new fuse in.

I've not added any new accessories. Any troubleshooting tips for someone with ZERO knowledge of how to troubleshoot a Merc would be much appreciated!

It would be useful to know if the fuse blows WHILE you are starting the engine or AFTER the engine starts.even by just a second or two. Obviously look for any pinched or chaffed wires or so forth that might be helping the problem. I am assuming that the fuse powers the ignition and/or the fuel pump since it won't start without it.
BTW, if you go the the auto parts store and buy a 15 amp circuit breaker that is the same size as your fuse it might make it easier on you to not have to replace the fuse after each try. I would not recommend using the breaker all of the time since any short that blows a 15 amp fuse could cause some real damage if it is not repaired.