Wanting to wire a bilge pump in a boat directly to battery. Bilge pump has 12 gauge wires. Two brown wires going to a three way toggle (one is for manual operation, other is for auto operation). From switch I want to put in an inline fuse (5 amp) but I can only find a 16 gauge inline fuse. So I thought I would connect the brown wires to the switch, then connect the 16 gauge inline fuse to the switch and heat sink it to a 14 gauge red wire to positive battery terminal. 12 gauge black wire from pump would heat sink with butt splice directly to 14 gauge black wire that would connect to battery. Is this safe or do I need to find a 12 gauge inline fuse holder and use 12 gauge wire throughout?

  • Is this an additional bilge pump? If not, why do you want to change the operation of it? What's the amperage of the pump?
    – JACK
    Commented Aug 6, 2020 at 16:25
  • 3
    I’m voting to close this question because this is about a boat not home improvement
    – Ack
    Commented Aug 6, 2020 at 16:49
  • Hi Jack, I'm actually installing the bilge pump in a cooler to make a live well. I appreciate the feedback you all have provided. Ack: I apologize, I'm new to this and didn't know this was specifically for home improvement. I'll be more careful about where I post questions in the future.
    – Todd
    Commented Aug 6, 2020 at 20:46

2 Answers 2


The big deal with DC is the distance using the larger wire as the feeder will reduce the voltage drop. You will be fine using the 16 awg wire in the fuse holder with the 12 awg. Suggestion if you use crimp connectors fill them with silicon sealer , even bathroom calking will work then stuff your wires in and crimp this will make the connections moisture proof and anyone that works on marine electrical knows how the connections corrode away if not sealed. I have used this trick on my boats regularly used in saltwater and have never had a bad splice even a decade later.


Depending on the type of wire, #16 is rated for at least 5A (often 10 or 13 depending on application). That's all that really matters aside from the quality of your connections.

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