Marine Ac/Dc attempts to answer your questions about boat wiring and marine electrical techniques, concepts, and products. We get lots of mail from folks in mid-project or who are just curious about their boat’s electrical setup.

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Hello Kevin,

I recently purchased an AFI 38000 2 speed wiper motor for my boat.

My boat doesn’t have a wiper, but has switches and wiring already. The problem is my boat wiring is for single speed wipers with Carling rocker switches for port and starboard with 3 prongs, grd,+ power,load- on-off.

I was wondering since I don’t have a heater if I could use that switch for the wiper. It is an ON-OFF-ON switch with 4 prongs, grd, load A, + power, load B, and it has a light built in it. I don’t know if I should connect the park wire to the + terminal, I’m afraid there might be a draw on the battery all the time.

If I can’t use that switch, do you know what switch I should use? I’d like to stick with the same design as the rest. Any help would be greatly appreciated.

Thanks,

Larry

Hi Larry,

You can certainly use your heater switch for the wiper. Connect your park wire to the + terminal and your speeds to A and B. If you connect both wipers to the same switch, they will not shut off properly. The speed wires need to be independently wired to keep them from feeding back.

If you want them on the same switch, I would use a DPDT switch like this one. It will allow independent switching of both wipers.

Hope this helps,

Kevin

Kevin,

I recently bought a used boat. It was improperly grounded and burned some of the boat wiring out. My mechanic repaired several problems, but one problem still remains.

When you switch on the ignition most gauges jump to their maximum. For example the trim is maxed out to the right no matter at what level the outboard really is. The oil pressure gauge does nothing. The tachometer goes clear to the right. The speedometer goes to about 10 miles an hour and stays no matter what speed the boat is moving.

Other electric things work correctly, such as the horn, the starter motor, the trim mechanism, bilge pump, bilge blower, and so forth. The stereo system, the marine radio, and GPS seem to be non-functional.

What is that it that can cause all gauges to fail like this? By the way, the boat is a 2002 Chaparral 180SE with a Mercruiser 3XL engine and outdrive. The boat has been badly mistreated, and has required a lot of work to get it functioning again.

Thanks for any suggestions you can give.

Steve

Hi Steve,

It sounds like you have a combination of marine electrical problems.

My guess is that you have more burned out wires.

You should start by checking for 12 volts at each gauge. + on purple and – on black

Then, using an ohm meter check the following

• Trim position – brown/white – 60 ohms down 11 ohms up
• Oil pressure – lt blue – over 240 ohms 0 psi 33 ohms 80 psi
• Fuel – pink – over 240 ohms empty 33 ohms full
• Tach – gray – test for continuity through harness to engine

As for the speedo, check for a plugged or melted pitot hose, if so, replace the hose. You should also clean up the pickup and check for a bent axle on paddle wheel

Hope this helps,

Kevin

Kevin,

My boat wiring includes a Guest 2623 marine battery charger, it is about seven years old and the middle lights for the charger no longer come on.

Does this indicate that the charger circuit is bad and a new one is in order?

Thanks,
Dana

Hi Dana,

I asked a friend of mine at Guest Marine Electrical about your situation. He wrote that, “…this may be just be the LED is going out and the charger is still good. You could check the output of the leads to be sure. The charger will go through its algorithm as long as it has output.”

In other words, you will want to test the output voltage with a digital volt meter to see if the charge may still be performing even though the lights are not on.

Hope this helps,

Kevin

Kevin,

I have been thinking about corrosion, road salt and +/- ground systems in relation to rust and basic electrolysis. It is interesting that marine electrical has already addressed these kind of issues.

So, would it be possible to build a custom wiring harness for a VW Beetle that would bypass the body ground a’la boat wiring?

Thanks,

Scott

Hi Scott,

Boat wiring harnesses avoid body grounds for two reasons:

1. To minimize galvanic corrosion
2. Most boats are not made completely from conductive metal

If you built a harness for your Beetle, you could certainly run individual grounds back to a ground bus instead of using the car body/frame. It would nearly double the amount of wire required for your project, but you would potentially eliminate electrical circuit problems caused by corrosion.

Kevin

Kevin,

Just came across your web page and it seems great. I couldn’t find an answer to my question, so here it is.

I have a 1992 Sea Ray 330 Sundancer. It has two 7.4Ltr engines and 3 batteries. I want to replace the stereo and add a chart plotter.

My question is where do you run the boat wiring? I assume you don’t just splice it to another wire. How do you know which battery you’re wiring it to? Is there a buss somewhere that you tie in accessories?

Thanks for any info,

John

Hi John,

Your marine electrical setup has one battery for each engine and one for the house systems – your stereo and chart plotter should be connected to the house battery.

If you are replacing the existing stereo, I would use the existing power wires. These probably run from the stereo to a main DC distribution panel in the cabin or to a breaker panel in the helm. Stereo power boat wiring has not changed color for years. You should have:

• Yellow (constant power)
• Red (switched power)
• Black for ground.

The speaker wires are:

• White-white/black,
• Green-green/black,
• Gray-gray/black
• Purple-purple/black.
• You may also have a blue wire from the stereo that is the remote turn on for an amplifier.

Finding power for the chart plotter may not be as easy. In your helm, there should be a ground buss for the negative wire. You will need to do some exploring to locate an adequate power supply. I would look on your helm breaker panel for an electronics or helm accessory breaker. If one is open, use it. Confirm that the breaker rating is the same as the rating required by your chart plotter manufacturer. If too large, install in in-line fuse at the correct rating.

If a helm breaker is not available, your two options are to piggy back your power from another helm accessory or run a new wire to the battery or distribution are. Either way, install an in-line fuse as close as possible to the power source to protect the wire and your new electronics.

My preference is to piggy back your power from one of the helm breakers. Most plotters do not draw an excessive amount of current and it is much handier to have all of your circuit protection in one location.

Please let me know if you have any questions,

Kevin

Kevin,

My current marine electrical system includes a Guest charger, Model 2615, and would like to install a Blue Seas 120 amp SI, ACR.

The ACR instructions state to connect the onboard charger to one battery. The 2615 can charge two batteries, is it ok to connect only one battery from the charger?

Thanks.

Pete

Hi Pete,

The ACR or any voltage sensitive relay system acts like a smart battery switch. As soon as one battery has a high enough voltage, the relay between the two batteries closes and connects the batteries together.

I would recommend setting up your boat wiring to connect both charger outputs to the battery in your system that has the most DC loads. The 2615 charger is older technology and may get confused with the relay in the middle.

Hope this helps,

Kevin

Kevin,

I am replacing a Sea Ray 225 Weekender ignition switch 4 prong with a new 4 prong.

I understand the boat wiring color scheme however there are two red and purple wires that are exactly alike that could be the battery or the assessory wire. The only difference in the two wires is that one of them has a white tag on it that says I 03.

Any ideas which goes to battery and which goes to accessory?

Andrew

Hi Andrew,

Unless the key switch breaks the connection between the ACC post and the BAT post when your are starting the engine, it really doesn’t matter.

You have two choices.

1. Use a meter and test to see which wire has constant 12v+. This wire goes to the BAT post.
2. Take a guess. You won’t hurt anything. If the ignition switch breaks the connection between the ACC post and BAT post during starting and your boat will not start, then you guessed wrong. Swap the wires and go boating.

Kevin

Kevin,

Why are ac and dc ground buses tied together in boat wiring? It would seem to be a possible source of electrolysis.

George

Hi George,

You are correct.

When you tie the AC and DC ground buses together, you definitely create the path for stray current corrosion through your shore power connection.

BUT

The wire provides a ground path in the event of an AC fault to the DC system in your boat wiring. Without it, your AC breaker will not trip. The path to ground would be through the boat’s DC system, through the engine, and through the water. There is too much resistance in the water to cause the breaker to trip. All DC devices would become energized at 115V AC.

It is probably better to corrode a drive than kill a friend. I always recommend keeping the ground buses tied together. So does the US Coast Guard and the American Boat and Yacht Council.

Kevin

Kevin,

I hope you can help me. I have a 1998(?) Starcraft pontoon (called Starfish 240 Classic) with a three position (OFF-RUN-START) push-to-choke ignition that I lost the boat wiring sequnce. I don’t know what color wires go on which prongs. Here’s what I have:

Boat Wiring Colors

• Yellow w/black stripe (connects to center prong…that’s the only one I know)
• 3 Purple wires



• 2 Black wires
• 1 Black and Yellow wire
• 1 Red and Black wire

Six-prong ignition markings (reading clockwise):

• C – is center prong
• M – top
• B – two o’clock
• M – four o’clock
• I – seven o’clock
• S – ten o’clock
• A – empty (no prong)

Thanks for your help.

Mike

Hi Mike,

See below. It appears that your are missing a yellow/red wire that would connect to the S (starter) on your key switch also.

Good luck,

Kevin

Boat Wiring Colors

• Yellow w/black stripe – connects to center prong
• 3 Purple wires – all 3 connect to the I post
• 2 Black wires – both to one of the M posts
• 1 Black and Yellow wire – the other M post
• 1 Red and Black wire – B