How to troubleshoot a boat wiring voltage drop

We received the following email from Jack about a problem that he is having with his Aqua Patio pontoon:

I have an on again off again electrical problem.

The boat is pontoon, Aqua Patio.  When boat was purchased the live well in rear had a factory problem.  the live well leaked over the switch mechanism; the boat yard rewired the system to a console accessory swich.  It worked for a few years but I am convinced it is a ground problem.

As soon as the motor receives current it works at a very low speed (not enough to pump).  The motor works when placed across the battery directly.  The voltage is 12 volts at the motor when turned on.  When the motor is hooked up and tested it may or may not work for a minute.  When motor is disconnected and the voltage remeasured the volt reading is somewhere between 2-6 volts.  I have voltage at the console but the same senario occurs when I connect and reconnect motor.

The boat is still out of the water so it is easier to track wiring.  It is so many splices because of the rewire that I hate to start cutting wires to isolate. The port and starboard rear courtesy lites I think do not work which are connected in the circuit.  Cell phone or portable courtesy lite receptacles are in the circuit (have never used but don’t think they work). The old switches that were part of the courtesy/live well circuits are disconnected and by-passed.

The new wiring to the console is blue to ground, the hot is brown.  The new circuit is connected to the black in 2-3 different places, of course, difficult places to get to, so dismantling is necessary.

Can you give me a starting point since it is difficult to trac this by yourself? Is there an isolation proceedure that can be done without cutting all the wiring?



This is a common occurrence on boats that are made of metal.  Godfrey Marine, like every other pontoon builder, does not use the metal framework on the boat as a ground.  This helps prevent stray current corrosion (galvanic corrosion), but causes strange ground problems like the one you are having.

Another problem that occurs on pontoon boats is when the boat wiring harness is not properly secured to the underside of the deck.  Even if properly secured, wires can be damaged even under normal use, e.g., the wires could be caught by the trailer or perhaps damaged during a “stunt docking” maneuver.  Whatever the cause, the boat wiring may now be able to make intermittent contact with the metal framework of the boat.  While the resistance is high enough to not trip the breaker or blow the fuse, it can still cause extremely low voltage readings under load conditions.

The best solution to your problem is to run two new wires to your live well pump.  Disconnect the existing wires.  Connect a new ground wire from the negative of the live well pump (usually black wire) to your battery negative or a negative buss near the battery.  Connect a new live well power wire from the positive of the live well pump (usually brown) to the accessory switch on your console.  I would recommend using at least a 16AWG good quality tinned copper boat wire.

This is my simplest solution to your situation.

Good luck,


Clever “QuickConnect” for DIY Pontoon Electrical

Several of our readers have alerted us to a very slick offering from the folks at Their new QuickConnect line goes a long ways towards alleviating the confusion (and headaches) caused by adding major electrical components to – or totally rewiring – an older pontoon boat.

Pre-loaded and pre-wired to make installation exceptionally easy, the Pontoonstuff QuickConnect system includes OEM quality gauge panels, switch panels, accessory harnesses, and even a deck-mounted light holder complete with sidelights, horn, and docking lights. And, as the name suggests, all of these parts are engineered to be quickly connected together by the boat owner.

It is obvious that a lot of thought went into this system, which is built from the highest quality marine grade materials. Everything is strictly first-class, from Carling switches and Faria gauges on the panels to the Attwood and AFI components in the light pod. All of these parts are then wired with the finest quality copper wire – tinned for superior corrosion-resistance. As you would expect, both the wiring and the circuit protection accurately anticipate the usual amp draw for each accessory.

This QuickConnect family of products assures that DIY electrical work can be done both quickly and safely – at least for pontoons. One wonders why a similar system couldn’t be offered for other types of boats?

Marine Circuit Protection

More great boat wiring advice from…

Any boat built to NMMA (National Marine Manufacturer’s Association) standards has circuit protection for its boat wiring system. These breakers/fuses are specified to provide adequate amperage for all standard equipment. And, the original boat wiring is sized for the factory installed system.

Problems occur when the boat owner or dealer begins to add other items.

The best and safest position to place your circuit protection is as close as possible to the source of power (battery or distribution panel). For example, a new fish finder is added to the helm of a boat. There isn’t an obvious way to splice in the existing boat wiring to connect the power and ground wires. The solution is to run a new pair of wires to the battery. The fuse for the fish finder needs to go as close as possible to the battery. The fuse is protecting the fish finder and its wiring. If the fish finder has an internal fault, the fuse will blow. If the wire between the fish finder and the battery gets damaged, the fuse will blow.

If the fuse is installed close to the fish finder, then in the case where the wire is damaged between the fish finder, the wire will burn instead.

Circuit protection is also very important when adding additional charging sources. This new charging source is considered to be a source of power that needs circuit protection. If it is not a “self limiting” device, circuit protection is needed at both ends of its positive output wire. Most chargers are self limiting.

For example, let’s say that a solar battery charger is added to boat. It has 4’ long leads with an inline fuse 7” from the end of the positive lead. The boat owner needs to add 8’ of wire to allow the charger to be connected directly to the battery. As long as the wire doesn’t get damaged, this setup will work fine.

Problems occur when the wire gets damaged. If the wire is damaged between the charger and the inline fuse, the self limiting battery charger will shut down, and the blown fuse will limit the output of the battery. If the wire is damaged between the inline fuse and the battery, the battery will continue to discharge until it is depleted or the shorted wire has completed burned up. This usually results in a fire.