Bilge pump short

[abaddorf]

Bilge pump on my 2005 SR1800 shorts out. After checking wiring connections from the pump and float, pump will initially work for a few seconds, then the 5amp fuse blows. I had an extra 20amp fuse, which I used, and the pump works. I only run pump for about 30 seconds, as I know I shouldn't be using this 20amp fuse.
Any suggestions as to why pump seems to work ok with 20 amp fuse but shorts out with the 5 amp fuse?

[mmwjr]

Most likely the pump is drawing too much current due to corrosion impending it’s ability to spin freely. Time to replace it.

[shrew]

Replace the bilge pump. Strip back the Pos. & Grnd and ensure their isn't corrosion in the wiring underneath the sheathing.

The fuse protects the wire from the power source to the device. It is not intended to protect the device itself, per se, but rather to prevent the circuit wires from overheating. You would need to increase the gauge of the wires in order to increase the fuse size.

The problem is more than likely corrosion in the circuit or connections.