blown fuse

[san dimas]

When my aluminum boat gets wet such as in a rain storm it blows a fuse and I lose everything on the dash board including my bilge pump. The engine continues to run fine. If the boat isn't wet everything works fine. Any ideas?

 

[Bass Tracker TX17]

Do you have an automatic bilge?
Is there water in the boat enough to start the pump when wet ?

 

[Silvertip]

It is very likely the bilge pump that is causing the issue since it is connected to the boat harness. When the boat is wet, the pump probably kicks in and the boat harness fuse is not big enough to handle the current requirements. Installing a larger fuse is not the answer unless the +12 and ground wires are large enough to handle that fuse. In a boat, the harness that feeds the console and all accessories except for the instruments is called the boat harness. The engine harness handles the engine, shift/throttle control box, and the instruments. If you do have an automatic bilge pump then it would be prudent to wire the automatic line directly to the battery through an appropriate size fuse.

 

[san dimas]

I don't have an automatic bilge pump. The fuse blows even if I don't turn the pump on. The 20 amp fuse that blows is on a red wire that is hooked to the battery. I'm assuming that this wire runs up to the fuse panel under the dash. If one of my accessories shorted wouldn't it blow just it's own fuse on the fuse panel instead of the 20 amp fuse by the battery?

 

[Silvertip]

If that main fuse is blowing then the problem is between the battery and the panel. Moisture is causing high current flow between the red and black wire. Look for cracks or charged insulation.

 

[san dimas]

Thanks silvertip. That's what I was thinking. I understand that a aluminum hull should not be used for a ground. Does that mean if a bare wire touches the hull that it won't be a problem? In other words, am I looking for a path between the pos. buss main feed and the neg. buss return feed between the battery and the fuse panel? Thanks for your help.

 

[gm280]

The only way the aluminum hull would not cause a problem is if the ground wire was the only one chaffed and touching the hull. If the positive wire was touching then anything else would cause fuses to blow as well. So you do have a problem with the wiring between the battery and the buss bars in my opinion. But if you do find a chaffed negative wire touching, I would either shrink tube it or replace it. An aluminum hull is not a good idea to be used as ground. JMHO!

 

[san dimas]

Thanks gm280. If a chaffed pos. wire is touching the hull will it short back to the battery thru the outboard motor? Is that why it will blow the fuse?

 

[san dimas]

If my main feed up to the fuse panel is 10 ga. wire, should I have a 30 amp fuse in line instead of the 20 amp fuse?

 

[san dimas]

I think I figured it out. It seems to blow the fuse when the automatic bilge pump turns on. I clipped the lead from the main wire to the pump to isolate it and no more blown fuses. I can still run the pump manually with the switch on the dash and I don't need the automatic feature so I'm hoping the problem is fixed. All the other circuits work fine. Thanks for all your help.

 

[san dimas]

I forgot to say that I didn't even know that I had a automatic pump.

 

[Bass Tracker TX17]

I forgot to say that I didn't even know that I had a automatic pump.

Well you know now...
Glad you traced it down. Might want to try and get that feature repaired.
Can come in handy.

 

[san dimas]

I think that's a good idea basstracker. I'm also wondering if maybe it's the alarm or alarm wiring that's the problem. I'm going to talk to my Merc. dealer tonight. All I know is the wire I disabled was carrying way too much current. When I touched the wire back together I could hear an alarm under the helm beep until the 20 amp main fuse blew so I'm assuming that alarm is water in the bilge. Maybe I'm wrong but the main fuse doesn't blow any more.