Short in bilge circuit

[mendocoast]

Hello All -
I acquired an '06 22' Cruiser recently and finally got around to doing maintenance on batteries, (2) Costco Marine Batteries. One was pretty well discharged while the other was in pretty healthy shape. As I started reconnecting wires I noticed that the bilge positive was sparking. There are aft and cabin bilge pumps. Not sure if that's a stock factory install - something I hope to learn from responses. At any rate I confirmed with multimeter that circuit is shorted - resistance drops to zero very quickly across circuit. Haven't found any clear in visible wiring insulation damage or loose connections (at pumps or switch block. Obviously this wiring is exposed to water on a regular basis. So I'm curious if these pump units are known to fail internally or if there are any other known strategies/hints for hunting this down before I start digging into harnesses or just re-wiring.

If you have any specific experience with this issue and/or these pump parts I'd love to hear about it. I have a background in electrical construction so I'm already aware of the fundamentals of troubleshooting shorts. But I am new to this boat and this is an opportunity to start getting acquainted with the wiring system. It's pretty spartan at first look which I appreciate.

Here are pics of the pump compartment wiring.
https://drive.google.com/drive/folders/1Hgu8mz672QnrHsyWKO6gMBaP5ptICw1k?usp=sharing

[thataway]

Thanks for having the photos easily available. The wiring at the pumps externally seems fine. Does you battery, which these pumps drain down rapidly? Do either of these pumps run properly when the "Bilge" switch in the console is activated?

Generally, I prefer to re-wire--and you will have to check to see if there is a short in the pump itself. It could be a devil of a time to trace the wiring to the console, and find a bad part of the wiring. The aft pump is when the boat is running, there is bow rise and the water in the cockpit drains aft. The pump inside the door (under a step?) is in case water gets in the boat when on a trailer, in a slip or on a lift. When the sits "level" the lowest point is the front end of the cockpit, and that is what the second pump is utilized for. One of the "+" wires to the pump is on all of the time, and generally is wired directly to the battery, or a bus bar near the battery, which will be easy to trace and replace. Us proper size butt connector, with adhesive shrink plastic, and put a cover of an adhesive shrink wrap over that connection, so it is totally water tight. The same for the inside pump--but it will be harder to trace down all of the wiring. Generally the boats come from the factory, with one bilge pump. The second one probably was added by an owner along the way. If so, it probably is not in the wire loom, and just electrical ties which hold that wire next to the loom. It is nice to have two different bilge pump switches.
The best configuration is for each pump; "Auto, manual. on/off"

[mendocoast]

I see now that circuit is auto/manual, so closed (hot) on auto. Pumps seem to operate ok. That explains what I was seeing with that + lead, and if there's a short that's just a coincidence. I may have a bad battery and/or a short there or somewhere else. I'll probably swap out battery and see what happens.

[thataway]

I would load test the battery and see how it holds a charge. Even some batteries which seem to be shot can be brought back to life, by slow charging, then do an equalization. Do you have an engine start and a separate house battery. If not I suggest that. Also a Voltage Sensitive relay. (VSC or ACR, same thing). The engine start is a #1 battery, the house bank is #2 battery. The VSC goes between the start and house battery. It cuts the circuit between the batteries when the voltage is less than about 13.4 volts, and does not re connect until 13.7 volts, and the start battery is in its charge phase. This protects the start battery from being drained during a night full of lights, TV Satellite etc... It also spares the electronics from a voltage surge or low voltage during the engine start phase.

A digital volt amp meter is an essential tool, Knowing how to use it is even more essential, and if you don't there are both books and Videos on what to do to become very familiar and competent in diagnosing electrical problems. All of our boats will have some gremlins in the electrical system. Be sure that all corrosion has been removed, and steps taken to avoid future corrosion. Pay attention to the ground (-) system (black or yellow wire--but don't mistake a black ground for a hot 120 lead.

[mendocoast]

I'm a licensed electrical contractor. I used to manage the construction of very large solar power plants. So, yes I have a multimeter. That's how I determined there was no resistance in the circuit in the auto position. I'm just new to this class of boat and the particular wiring on this one.

[gulfcoast john]

[thataway]

ABYC: is the boating standards organization. Here is their color coding:

Color Red = DC Positive Conductor, Positive Mains

Black or Yellow= DC Negative Conductor, Return, Negative Mains

Green or Green w/ Yellow Stripe= DC Grounding Conductor. Bonding System, Bonding Wires (if insulated)
Light Blue=Oil pressure
Dark Blue=Cabin & Instrument Lights
Brown=Generator Armature or Alternator Charge Light
Brown=Fuse or Switch to Pumps

. Here is the ABYC general boat wiring code

Unfortunately not all engine manufactures follow a standard code:
Here is the outboard wiring harness code:

It is worth while printing out these codes and keeping them in the manuals and papers you have for the boat. I keep mine in clear plastic sheets in 3 ring binders.

mendocoast, I often give some basic instructions, since I find may new members of C Brats have little knowledge in DC circuitry. In boats we rarely find short circuits, because all circuits should be fused; testing for blown fuses is the first step in trouble shooting. Most commonly we find low voltage due to increased resistance as a result of corrosion.

The original bilge pump will have 3 wires, ground (-), manual on (+) and auto on (+). Some bilge pumps only have positive and negative; some these pumps have a built in circuit to turn the pump on every so often, check for water, and leave the pump on until any water is gone-These will run down a battery fairly quickly.

[kennharriet]

For my rewire project I ordered this tinned bilge pump wire and will use waterproof heat shrink connectors. Also have a new Blue Seas fused switch panel powering the mid bilge and a 24hr fused switch mounted in the stern for the aft bilge.

https://tinnedmarinewire.com/product/14-3-awg-bilge-pump-cable-sjtow/