For several years I've had an automatic bilge pump rigged in my dock dinghy, that I use to access my sailboat that is on a mooring. It's powered by a battery in a box (sealed 7-AH gel battery like they use as alarm system backup). I take it home to charge occasionally and alternate 2 batteries.

The other day I found the boat filled with water. The only times that's happened is when careless about charge interval and we have heavy rains, or when something prevents the float switch from moving. Not this time...

I opened the battery box and the first thing that struck my eye was this fuse holder. I cut this off and got the spare battery and tried the pump -- the motor did not fire with the float switch in the up position. Cut the switch wires and tested for continuity -- the switch worked on/off as it should. Replaced the pump with a new 360gph Rule and put on a new fuse holder and all is good.

The wires and crimp connections throughout the circuit had a good appearance (no melting) except at this fuse holder.

So I'm still a little puzzled, and feeling quite lucky this didn't start a fire at the dock. What puzzles me was even if I over-sized the fuse, why did it melt at this assembly without blowing the fuse?

(BTW my new replacement fuse is 2.5A)