November 29th, 2010 by Kevin Hannula
This site attempts to answer your questions about fishing 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.
There are loads of post already on the site which we hope you will browse through. If you’re trying to track down info about a more specific category, please use the search box in the upper right of this page or check out the list of various subjects farther down on this page.
If you aren’t able to find the info that you need to complete your particular fishing boat wiring project, please send us an email at firstname.lastname@example.org.
Thank you for visiting. We look forward to hearing from you and hope that you will be able to come back often.
December 9th, 2013 by Kevin Hannula
My fishing boat wiring includes a Guest 2611a Charge Pro Boat Battery Charger.
It has worked great for years but I need your help to get it charging again.
During a recent vandalism at my marina, the charger's A/C cord got cut off.
Could you please tell me how to reconnect everything? That is, I need to know what wire is what color. There are
four wires altogether.
I'm sorry to hear about your problem. The good news is that it shouldn't be
too hard to repair.
The Guest chargers use the international wire color code.
So in your case...
- Brown - AC hot - to your black
- Blue - AC neutral - to your white
- Green - ground - to your green or unshielded
Hope this helps,
November 8th, 2013 by Kevin Hannula
Tonight I ran into a very odd boat wiring issue.
I have a 2002 Proline Sport 20CC with a 150hp Mercury outboard. Traveling along in
the fog, my motor started to trim itself up and out of the water - all by
itself! One thing I noticed is when the motor would trim up the bilge
pump came on as well. (No water in the bilge, by the way)
My guess is
a common short.
What should I look for in tracing this short?
It could be a ghost. It is that time of year.
BUT, it is probably a short between the trim power wire (red) and trim up wire (blue) and bilge power wire (brow) near the shifting mechanism on your helm.
It is common for wires to be pulled tight to the shift cables. They have some movement when the shifter is actuated and eventually wear through.
Hope this helps,
Haha funny you say that. With the fog rolling in, the lack of visibility, and the boats mind of its own it was like out of a horror movie! I was waiting for a pirate ship to pull up out of the fog! Lol
Anyway I did some troubleshooting this morning and found the trim switch on the motor was passing power through it on the up side even when not depressed. Luckily the problem happened while I was troubleshooting. When I press the trim up on the motor and let go it would continue to trim up for a second before stopping.
When checking with a volt meter. Trim up pressed would pass about 12.6v and when let go would go down to 12.3v and slowly trickle down to about 11.3v. Up side was fine and passed no power if not depressed. So I disconnected that switch and only used the throttle trim switch and it was responsive and stopped without delay when I let go of the button. So it looks like a bad trim switch at the motor.
But it doesn't explain why the bilge came on too, lights and fish finder flickered when that happen also. I left the motor's trim switch disconnected so I guess only time will tell if that was the only problem.
Thanks for your help! I appreciate the quick response and assistance!!
October 28th, 2013 by Kevin Hannula
I have 1992 Smokercraft Pro Mag, with a 1992 Mariner 90HP two stroke oil
injected engine. I bought the boat used about 2 years ago.
At first, the tachometer and the gas gauge were working fine. But, now neither one of them does anything whether the engine is running or not.
The tach does not "flatline", instead, it is reading somewhere in the middle of the dial regardless of
whether the engine is running - or if the key is even in the ignition.
Do you have any idea how to fix this?
Are the two gauges on the same wiring or the same fuse or circuit?
I have not tried to do anything to fix them yet, but it is becoming a real pain to operate the boat without a gas gauge, always guessing at how much is in the tank.
Thanks for any assistance you can provide.
Both of the gauges are powered by the same wire.
- Power for the gauges will come from the purple wire.
- Ground for the gauges will come from the black wire.
- The source of the purple wire is the key switch.
- The dash will have a common ground.
This should be easy to fix,
October 1st, 2013 by Kevin Hannula
I’ve heard in the past and as recently as last night that “dc won’t shock
Well, I’ve grabbed a plug wire at the plug and can report to you that the DC electrical system is standing tall. I had a brain fart prior to grabbing that wire.
But as to the truism, maybe I am missing something? What are these people talking about?
As you proved through your careful experimentation,
DC can shock you. The determining factor is whether or not the voltage is high enough.
Boats run on 12 volts (some at 24 volts). Your internal resistance is too high to allow for a noticeable discharge through your body.
But, on an ignition system, the DC voltage can be as high as 30,000 volts. (2,500 times as high as your normal boat wiring). It is easy to discharge 30,000 volts DC or AC through a body.
Hope this helps to clear things up.
August 12th, 2013 by Kevin Hannula
I just found your site, Thank you! There is a lot of useful boat wiring info here, especially for those of us who are not near to nor have access to a marine or ABYC electrician.
Hopefully you can help me with my questions, there are a few.
I have a 1998 Grady White 272 Sailfish which did not come with shore power, only the usual
marine electrical components, pumps, refrigerator, wash down, macerator, etc. The boat is currently on a trailer in my driveway until I finish repairs and I am sure it is safe to put back in the water.
After reading Charlie Wing's book and numerous online articles I added shore power. Starting at the transom with...
- 30 amp stainless outlet, to 30 amp double pole breaker within one foot of outlet
- Green ground to galvanic isolator then
- All three marine grade 10gauge wire goes twelve feet to cabin where it
- Connects to a Blue Seas AC panel #8409, double pole disconnect with
amp/volt meters, reverse polarity indicator and three 15 amp circuit breakers.
- Black to hot, white to neutral, green to ground.
- 1st circuit to GFCI outlet in head (12 gauge wire)
- 2nd circuit to GFCI outlet in galley (12 gauge wire)
- 3rd circuit to Pro Mariner Pronautic 1240P battery charger (14 gauge Wire).
- Wire from 40 amp charger to batteries 6gauge. with 50 amp fuse each line.
Now for my questions.
- I do not have a negative ground bus in the aft compartment which contains
three batteries (1 house, 1 each for the outboards), switches, charger, main wiring for the outboards. Each outboard
negative. goes directly to it's own battery. Charger instruction's want the
charger case stud attached to engine block or DC ground buss with wire no
more than one size smaller than charging leads. Since the only negative ground bus
is under the cockpit controls (dashboard) and it would be difficult to run
this wire to the outboards, can I connect the case ground of the charger
directly to one of the battery negative terminals (All battery negatives are connected together). they all end up together anyway don't they?
- If I understand correctly, ABYC code wants DC negative connected to AC ground (green). Can I use the battery
negative terminal and wire to ship side of the galvanic isolator? Again it
seems however these wires are connected they still end up together. If this
is acceptable what would be the correct size wire from DC negative to the AC ground?
- Here is the strangest question I have for you. It makes no sense and would seem impossible.
When I take a voltage measurement between the hot wire and neutral, or hot wire and ground at the
GFCI, all is correct at 117v, but when I test hot to anywhere on the boat be
it a screw which is not touching any metal only fastened into wood or
fiberglass, a hose clamp around a hose to toilet, the DC refrigerator frame, or just the fiberglass or gelcoat I get voltage readings.
With the hot lead of the volt meter in the hot side of the outlet and the
negative side of the volt meter touching a screw (screw is only into fiberglass I took the wall apart to check ) I am getting a reading of 60+ volts. As I test screws further away from the outlet with the
negative, the voltage reading drops. Just touching gelcoat the reading is around 20 volts.
This happens at all outlets.
I also tested the outlets with a GFCI push button tester, lights lit up properly and the circuit tripped when the button was depressed.
What do I have incorrect or what could be causing the voltage readings?
Those are excellent questions about a subject that warrants a lot of concern
because of the risks involved. Here are my thoughts on each of the three.
- Yes. The battery negative chain would be a great common ground.
- My preference is to run a 10 AWG green wire from the galvanic isolator to the AC ground bus at your AC panel.
From the AC panel ground bus I would run a 10 AWG green wire to the DC negative. In your case this is either the bus under the helm or the battery negative.
Since the greatest chance of an AC fault is from AC hot to AC ground I would rather have the fault path more direct (to the panel, through the GI, and to the dock) instead of back to the AC panel, to the DC negative, and then through the GI to shore.
- I asked a friend of mine for his opinion on this one and I believe that
he may be right. The crazy readings may be from the high input impedance of the voltmeter. As soon as a load is added to any of these circuit combinations (AC hot to screw) the voltage
should drop to zero.
July 23rd, 2013 by Kevin Hannula
I am in need of your help with my boat's 24 volt trolling motor wiring.
I have a problem using my 70 lb. trolling motor at full power. It shuts down and I cannot use it.
The motor is wired using a Marinco 24 volt plug and receptacle. I talked with Marinco at one time and they told me the jumper in the plug was under sized but they had no corrective parts.
Any ideas of what has happened or what I can do to get this system running again?
Thanks for your help!
One option is to use only two of the terminals in the Marinco plug and do the 12/24 jump at the battery.
Basically, there is a wire from the plug to the negative of Battery 1 for the ground and a wire from the plug to the positive of
Battery 2 for the 24v positive connection. This lead has circuit protection at the battery. A jumper between the positive of
Battery 1 and the negative of Battery 2 is added to create the 12/24 system. This wire should be made from the same size wire as the long trolling motor leads.
Hope this helps,
July 23rd, 2013 by Kevin Hannula
I have a Crest 2003 Family Fish Pontoon with a 75 HP Mercury engine.
Recently, the 20 Amp Starter/Accessory/Trim fuse began to blow. I took the boat into the dealer where it was purchased and they spent ~$400 to tell me that the engine wiring was A-OK, but they could not fix the problem.
The hardest part is that the fuse will not blow unless the boat is in the water. I have tried to duplicate everything leading up to the blown fuse while running the engine with a water hose connected and have not been able to get it to fail.
Then I put the boat in the water and 10 to 90 seconds later (after putting it in gear), it blows. I lose the instruments, trim, but the engine continues to run fine. If I shut down, I can not restart without replacing the fuse.
I tried on land to ground the pontoons to see if that was it. Then I sprayed water on the wiring from the engine to the controller (rests on top of a pontoon). I removed the gas level transmitter. I removed the live well pump. I tried everything I could imagine.
I know this fuse enables power to the starter relay, and the up and down trim relays. They were checked out by the shop and found to be OK. I also measured the running voltage on the rectifier at 14.8 amps with the engine throttled up. The boat is simply instrumented: Tach, voltmeter, fuel gauge and that's it.
Sure could use some sound advice.
At the key switch, disconnect all wires connected to the A or I terminal. These should be purple. This will cut power to your gauges and anything else connected to the key.
If your key switch is incorporated with your shifter look for the purple wire coming out of the control. The motor will start and shut down without a problem.
If the fuse still blows, look for a bad spot in the wiring between the engine and the key. If it doesn't, then the problem is in one of the accessories connected to the key switch. It could be something as crazy as your stereo or tachometer.
Hope this helps
June 17th, 2013 by Kevin Hannula
This may be a stupid question and a stupid idea, but here goes.
I need to rewire my boat for a bigger trolling motor. Right now there are two
#8 positive wires and two #8 negative wires running from battery area to where trolling motor plugs in.
The trolling motor manufacturer says that this model of motor requires #6 wires.
Can I attach the two #8 positive wires to a heavy duty marine buss terminal located by plug
in receptacle and then a short piece of #6 to tie into receptacle? And do the same for negative side with another buss?
It is not the best solution but it would certainly work fine. Make certain
that you have the correct circuit protection in the positive lead at the battery.