Main 30 amp fuse blowing

[kpk]

Hi, i am new to the grady world. Just bought a used 2002 marlin with twin f225 engines. It has been running well and i am looking forward to doing the winterization myself. As i was about to have the boat pulled my starboard engine blew the main fuse after i lowered both engines. We replaced the fuse with the battery off, but it blew when the battery selector was turned on. I was on shore power with a battery charger at the time. The next day i disconnected from the shore power, replaced the fuse and the engine started and ran with no problems. Could the battery charger be causative? Why only the starboard engine?
Thanks kpk

 

[HMBJack]

Not sure but I think your house bank runs off, and is wired to, the starboard engine.

I had this happen to me and found my AC shore power plug and socket on the cord was burnt. Not sure why but it caused resistance. Once I replaced it, all was well again. Also - are running some high amp appliances alot? Like a microwave, hair dryer, stove or electric heater? That may offer a clue. Good luck. It's probably something simple and you'll eventually find it.

 

[Tucker]

Check all your grounds.

 

[kpk]

Thanks for the replies. I am not running anything as yet on the Ac except the air conditioner. Question though, is it possible for a line side short ((upstream from the fuse, toward the batteries) to blow a fuse? I thought only shorts on the load side would cause enough current to blow the fuse, so things like connectors and the next in line is the starter and then the rectifier regulator?
Thanks again,
Kpk