Boaters Guide to AC Electrical
Many seasoned boaters have an aversion to using AC Electrical around boats in marinas.
Water. Electricity. That’s a natural concern.
Marinco has been designing, building and supplying the best marine AC electrical products since 1972. Safety is always the first concern. And the best way to ensure safe shore power product usage is through training and education.
Marinco makes it easy to know how to use these products. They publish a great booklet entitled: “Boaters Guide to AC Electrical”, known around the marketplace as the “Shore Power Manual”. It’s the definitive resource when it comes to shore power. This guide drills out the mystery and concern, with straight-forward, easy-to-understand tips on AC Electrical.
You can order this booklet by visiting their website: http://www.marinco.com/view/96/guides
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
On-Board Charging
It started out promising to be a great day.
Gear is loaded. You’re at the boat launch or marina. Wife and kids are ready to go. And then…
…You turn the key…nothing happens. Dead battery. Now it’s now a lousy day.
We all have war stories of preparing for a great day of boating or fishing, only to get snagged by boat batteries that somehow died since the last boat use. No rocket science here. Know this: batteries lose 1% of their charge each day they are not used. Boats often times sit for long periods between uses. You can do the math.
There is a better way. If you have not embraced the concept of on-board charging, you need to. It’s simple … buy, install and use a marine-grade battery charger. The technology has come a long way. While the boat is either trailered and stored in your garage, driveway or wherever, you leave it plugged in. So instead of discharge between boat uses, your batteries are well maintained and healthy.
Today’s 3 stage chargers recognize when the battery is fully re-charged, and then go into “maintenance” or ”float” mode. That keeps it topped off…so when you’re ready to boat, the batteries are ready to crank.
The Guest range of on-board battery chargers are simply the most reliable, best performing and longest lasting products in marine electronics. Check ‘em out!
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
Best of both worlds — Guest Chargers + BEP VSR
The Guest range of Charge Pro Plus chargers combine reliable Guest charging with state of the art BEP voltage sensing. The benefit for the boater is simple…you can charge your batteries while on the water (DC to DC) as well as the normal AC route. The BEP VSR module is integrated into the marine electrical system and simply sends alternator current to where it’s needed most while you’re underway. Sort of like a charging traffic cop deciding where to send the juice. And it’s seemless to the user. You get to do what you should do…fish, boat and have fun.
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
Tsunami Bilge Pumps
Tsunami pumps are durable and designed to last, too.
The efficient design circulates water around the pump motor housing, helping to absorb the heat given off by the operating motor. Attwood uses the most advanced material available, including the best quality bearings and state-of-the-art brushes, alloys and magnets. Their patented shaft seal centers directly on the motor shaft, preventing leaks caused by misalignment.
Attwood’s exclusive molded two-wire seal is permanently fused to the insulation to prevent a leak path. And their wiring is caulked and tinned to eliminate wicking, prevent water damage and resist corrosion.
The Attwood Tsunami bilge pumps are available from the boat wiring specialists, EzAcDc.
Possible to salvage old switch panel?
Hi Kevin,
I recently purchased an older runabout on which none of the switches seem to be working.
While there seem to be a few switch panels available for sale on the web, none appear to be anything that would fit on my dash. I checked with my local dealer about fixing the existing part, but he is quoting more for the job than I paid for the entire boat!
Can you give me any advice as to how I might be able to do this job myself? I have had a little experience with electrical work, but the “rat’s nest” that I’m finding behind this panel is fairly intimidating.
Thank you in advance for any help that you may be able to provide.
Switchless in Seattle
Dear Switchless,
Unfortunately, what you are describing is an all-too common situation with older boat wiring.
The problem often started with an old-line boat manufacturer who used inexpensive, highly corrosive wire while paying no attention to standard boat wiring practices – like using consistent boat wire colors for specific functions. The good news 
is that these sort of builders are usually (thankfully) no longer in business – the bad news is that someone, i.e. you, are now left to clean up their mess!
Compounding the problem, this already bad situation can often have been made worse by a series of boat owners either trying to fix the builder’s original mistakes or making sloppy boat wiring modifications of their own. Either way, the end result is often a boat wiring system where, at best, wires colors do not match and that does not work correctly – and, at worse, something catches on fire.
Up until recently, your only option was to rewire each circuit individually until all of your desired components worked. To do this properly, you would use the appropriate wire color for each individual component.
A more convenient solution might be a slick new system from EzAcDc that I saw for the first time just last week. What these guys have put together is a top-quality harness that can be used to completely rewire your existing switch panel.
The EzAcDc system appears to have all of the wires and circuit protection that you would need for your project. Once you are finished, you can connect the rewired panel to your current boat accessory harness or, if that is in as bad a shape as your panel, EzAcDc even offers complete boat wiring accessory harnesses that are terminated to be plug compatible to the repaired panel.
I hope that this is helpful.
Kevin
Connecting two batteries with different capacities
Hi Kevin,
Many thanks for making this service available – reading the previous posts has been a real eye-opener.
I have what I think is a silly question, however I’d like to check:
I have two batteries, both lead-acid sealed 12 volt. One is a 70 amp/hour, which wasn’t up to the job of providing enough current
to turn the engine over in the mornings after sleeping over on the yacht. So, I went out and bought a 110 amp/hour which is.
I’d like to use both of these batteries – with the large capacity to run the boat systems and the smaller as a reserve / starter battery. The wiring to a main switch that allows Battery1/Battery2/neither /both is in place.
I think that I can simply connect the two batteries despite their different capacities, so that when ‘both’ is selected they will discharge together and/or charge together.
I believe that if one has a higher voltage than the other at the point of selecting ‘both’ then the higher will discharge to the lower until they are equal. I don’t believe that the fact they both have different maximum capacities will affect their use.
Am I right? Is there any drawback to connecting two batteries of different capacities?
Thanks!
Evan
Evan,
You are correct. You can certainly connect two batteries with different reserve capacities in parallel with your battery switch. 
You may want to consider modifying your boat wiring system by adding an emergency paralleling VSR like the one from BEP Marine instead of the battery switch.
This switch will automatically parallel the batteries when the engine alternator is charging the system. When the system is not charging and the voltage is below 12.6 volts, the circuit will open up. This device also offers an emergency paralleling feature that can be manually operated or remotely from a button.
Thank you for writing.
Kevin
Reconnecting a complex marine electrical system
Kevin,
I just purchased a boat with a fairly complex electrical system, which was disconnected.
I am trying to piece it back together again with an incomplete
wiring diagram. Some components have been added, removed or changed since the original diagram. In addition not of the components provides documentation for this full scale system.
The system is comprised of
- One engine battery (actually 2 6v serial),
- One house battery (also 2 6v serial),
- Solar Panel with Solar Regulator, Alternator,
- Battery Isolator,
- Heart Inverter/Charger
- Dockside AC.
I would love to see a sample wiring diagram for this type of system if one exists anywhere. If not, my biggest question is where to ground the AC? I have read conflicting information regarding whether the AC & DC should be grounded to the same common ground.
Can you shed any light on the subject and/or direct me to resources that might be helpful?
Dazed & confused,
Andi
August 19, 2008
Andi,
I have never found a great resource for boat wiring diagrams. It usually comes be piecing together schematics from several sites.
One of my goals for Easy Ac/Dc is that perhaps someday this site will become a no charge repository/library for this type of boat wiring information, which would be a real aid to all of us who work with marine electrical.
So, if any of the readers know of a source for diagrams and schematics – or, if you would be willing to contribute a few of your own – please send me an email. If everyone contributes just a little, the amount of material available to all of us should be impressive.
On a more helpful note, please check out the Guest battery isolator manual. This should help you to correctly connect your battery isolator.
AC Ground
- All AC ground green wires are connected at your AC distribution panel.
- The AC ground and AC neutral are not connected.
- The AC ground should be connected to the DC ground.
The main reason for this arrangement is to trip an AC breaker if there is a fault between the AC and DC systems on your boat. Without this connection, when a fault occurs, all metal components connected to the DC system will become energized at 120v ac. There is too much resistance in the water and no direct path back to AC ground to cause the breaker to trip.
I hope that this is helpful.
Kevin
Wiring a switch to monitor two fuel tanks
Hi
I wonder if you can help me. I am trying to wire up a switch for a fuel gauge on my boat.
There are 6 terminals on the switch, three positions on the switch off port tank and starboard tank. There is one wire from each sender on the tanks, two wires from the gauge and it appears there are two live wires.
Could you please advise which terminals are for which wires?
Thank you for your help.
Gary
August 18, 2008
Gary,
You can easily wire your single fuel gauge to both fuel tanks using the switch you are describing.
- You will need to supply 12v power (usually purple) to your fuel gauge. This will connect to the B+ terminal on the gauge. You will also need to supply a ground (usually black) to your fuel gauge.
- Connect a wire from the sender (S) terminal on the back of your gauge to the center left terminal on your switch.
- Connect the wire from the port sender to the top left terminal on your switch and the wire from the starboard sender to the bottom left terminal on your switch.
The gauge will be powered by the 12v power of your ignition switch. The switch will select which tank the gauge will read.
If you would like to have the switch turn off the gauge, you will need to reroute the 12v power wire to your fuel gauge.
- Remove the wire from the B+ terminal on the gauge.
- Connect the 12v power wire to the right center terminal on the switch.
- Connect a jumper wire from the top right terminal to the bottom right terminal.
- Connect one final wire from the top right terminal to the B+ terminal on your gauge.
The switch will turn the gauge on and off and on depending on the position of the switch.
Hope this helps,
Kevin
Will polarity affect compass light?
Kevin,
I am replacing a failed lighted boat compass with a duplicate.
The old one has 2 black wires attached to a disconnect type plug, but I don’t know which wire is positive and which is negative. The new compass has the wires labeled. I would like to wire the new compass using the old plugs.
Since I don’t know the polarity of the old wires, what will happen if I hook up the wires in reverse? Will it blow the light, the fuse or simply not work?
Thanks
Larry
Larry,
If the new compass light is a traditional incandescent bulb, then polarity is not a problem. If it should be an LED without reverse polarity protection, the LED will blow when it is hooked up backwards.
Typically, accessories that are lit with LED include reverse polarity protection. Hooking them up backwards means that they simply don’t work. When this occurs, just disconnect the wires, reverse them, and you should be ready for night time navigation.
In general, most compasses have incandescent lights, so you should be good to go!
For future reference, standard boat wiring designates black as ground and dark blue as instrument/compass light positive. Some boat wiring systems use yellow as their ground.
I hope that this is helpful.
Kevin
Common ground with two alternators?
Kevin,
I am wanting to have two separate alternators, one to use for my existing power system and a second to use to run an inverter for my 120 volt system.
Do I tie the grounds from both of the alternators together? If I have two alternator/battery systems would these not have to be isolated from each other?
Thanks,
Freddy
Freddy,
Tie all you DC grounds together. The best practice on 12v boat wiring is to have a common ground. Keeping the positives isolated helps prevent the dead cranking battery problems associated with inverter use.
A great option to add would be an emergency parallel VSR like the one from BEP. This would allow you to crank your engine off of your inverter battery or run you inverter off of your engine battery in an emergency. Plus, if the paralleled voltage is too low, the built in timer will open the circuit in 5 minutes to prevent complete battery discharge.
I hope that this is helpful.
Kevin
