Forward or reverse blows the ignition fuse. Need advice.

[infy]

I've been searching for a solution here and I've seen similar topics but nothing yet that matches.

1990 Avanti 2955 with twin 305 engines.

The engine starts and runs, revs up, and idles with no problem. But as soon as I move the throttle in to forward or reverse the port ignition fuse pops and the port engine stalls. I can reset the fuse, start the engine again, but as soon as I touch forward or reverse that fuse just clicks again. I'm stumped. Why would this be happening?

Starboard engine is fine.

 

[NHGuy]

EFI or carb? Bravo or Alpha?

 

[alldodge]

Could use a bit more info as NH mentioned.
Is this the 20 amp fuse behind the helm, or the another?

 

[infy]

Carb. I'm not sure if it's alpha or bravo. Engine serial number is: 0C761486

Yeah, it's the fuse at the helm. The port battery indicator isn't responding. It's basically showing the battery has no charge. I don't have a tester here with me to check the battery itself.. but if that port battery is out, and the only battery available is starboard, could that cause the fuse to pop?

I had both engines running at the time. I didn't test with only port running and in gear.

But in theory, could this be the result of insufficient electrical power?

 

[alldodge]

Not seeing anything which would cause a fuse blow in shifting normally. I would look around the shift plate to see if something is rubbing and wires fraying. Otherwise this did come up with another user and it turned out to be the wires being mounted next to the shifter. The cables had rubbed thru the wires and causing it to short out

 

[infy]

At first I didn't think these two issues were related but it sounds plausible. I took it out with a friend yesterday for about 4 hours. Midway the batteries were completely flat. Starboard engine was running OK so we turned around and headed back to dock.

I suspected a bad alternator. But if there's a short there that may be draining the system.

 

[alldodge]

Does sound like two different issues. A battery going dead is either a bad battery or charging system. The ALT can have a shorted internal component and cause the ALT to drain while not in use, and also not charge to full.

The blowing a fuse when going into gear is another issue as I see it. If it was blowing the fuse when going out of gear and if you had an Alpha drive then maybe something else

 

[infy]

Is there any risk to leaving the engine battery power on and shore power + charging system on? I may have accidentlly done that last time I docked. Hoping I didn't do any damage to the charging system.

 

[alldodge]

Is there any risk to leaving the engine battery power on and shore power + charging system on? I may have accidentlly done that last time I docked. Hoping I didn't do any damage to the charging system.

This is the way I leave mine at the dock every day during season