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Author Topic:   Problem With Electrical Distribution
Emilio Samtor posted 05-27-2010 09:49 PM ET (US)   Profile for Emilio Samtor   Send Email to Emilio Samtor  
I own a 2005 McGregor 26 sailboat. I had a Standard Horizon CP150C installed in my boat. I recently moved my boat to British Columbia, Canada and to my surprise my GPS unit did not power on. Although it is an old model it is brand new. I am the original owner and never had the opportunity to use in the lakes I sailed in the Prairies.

I took the GPS and chart plotter for inspection with a Standard Horizon licensed service shop in Vancouver, who checked the unit and found no problems with it.

I took it back to my boat and it still did not power on. This clearly indicates that there is a wiring problem. Because my boat is presently docked in a remote place I cannot get an electrician to check my wiring. So I have to find a solution on my own.

I opened the side of the cockpit to check the wiring to the GPS plug and [the wiring] looks OK. I went all the way to the battery connections and they also look OK. I visually checked the fuse box connections and also look OK. I am by now completely puzzled about what could be the source of the problem. Any suggestions and ideas to help solve this problem are greatly appreciated.

jimh posted 05-28-2010 07:40 AM ET (US)     Profile for jimh  Send Email to jimh     
While making a careful visual inspection of electrical circuits is a good way to locate problems which have occurred when there is a clear physical manifestation of the problem, a visual inspection cannot always detect a bad connection.

To test an electrical distribution circuit, begin by testing for voltage at the source of the voltage. Move along the distribution circuit with your test voltmeter, checking for voltage at each point in the electrical distribution where there is any sort of connection from the source. You should be able to easily located a bad connection in this manner.

Jerry Townsend posted 05-29-2010 01:27 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
You state that the wiring looks OK - in several locations. But by looking OK doesn't necessarily cut it.

One can often find a problem by drawing/sketching a wiring diagram of the wiring - as built. This sketch doesn't have to be fancy - or to scale, just showing the wires and the components in the circuits. With a sketch, the problem often just kinda "leaps" out at you.

Using a multimeter as Jim suggested is a good, and necessary step, in troubleshooting electrical problems.

Doing the sketch first - and noting the voltages you measure on the sketch also really helps. ---- Jerry/Idaho

jimh posted 05-31-2010 11:10 AM ET (US)     Profile for jimh  Send Email to jimh     
I agree with the recommendation to make a sketch. Based on reading technical literature for 50 years, the sketch should follow these conventions:

--the positive circuit is drawn along the top
--the negative circuit is drawn along the bottom
--the voltage source is drawn to the left
--the circuit flow is left to right for positive current

Here is a sample of a sketch of electrical distribution on a small boat from the battery to a device. I have added callouts along the circuit in order to make it possible to refer to various points in the circuit:

Schematic diagram of electrical distribution typical of a small boat

To test this circuit, connect a voltmeter as follows:

--connect the negative lead of the voltmeter to Z;
--connect the positive lead of the voltmeter to A.

You should read the battery voltage. For advice on battery voltage as a function of battery state of charge, see a separate article on that topic at

Battery Charge

We proceed with the assumption you measure 12.8-volts between A and Z.

Now, disconnect the test meter positive lead from A and connect to B. You should again measure the same voltage, 12.8-volts approximately. Proceed to test all points shown in the positive distribution, moving your test meter positive lead in sequence from A to B to C and so on, on to K. If at any point you fail to measure the battery voltage, you can investigate the circuit more closely for a discontinuity in the circuit that would interrupt current flow.

If you reach all the way to point K and still have an indication of positive voltage, reconnect your voltmeter as follows:

--connect the positive lead of the voltmeter to A
--connect the negative lead of the voltmeter to Z

Confirm the voltmeter still shows 12.8-volts (approximately). Now move the negative lead of the test meter to points Y, X, W, V and U, again checking to see that the voltmeter shows the proper reading. If find any point where the voltmeter reading changes, carefully inspect that portion of the circuit for any discontinuity.

jimh posted 05-31-2010 11:36 AM ET (US)     Profile for jimh  Send Email to jimh     
Emilio writes:

"Any suggestions and ideas to help solve this problem are greatly appreciated."

Acknowledgment of suggestions and ideas to help solve your problem are also appreciated.

jimh posted 05-31-2010 12:31 PM ET (US)     Profile for jimh  Send Email to jimh     
A good example of electrical distribution problem diagnosis is given in an article in the REFERENCE section:

Electric Starting Circuits

The article identifies 53 points in the engine starting circuit where there could be a discontinuity.

jimh posted 05-31-2010 12:33 PM ET (US)     Profile for jimh  Send Email to jimh     
A good primer on the electrical distribution system used in most small boats is given in another article in the REFERENCE section:

Boat Electrical Circuits and Wiring Practices

The article explains the normal practices used in small boats to distribute electrical power from the battery to accessory devices.

64nauset posted 06-13-2010 11:14 AM ET (US)     Profile for 64nauset    
I just ran into this thread today and would like to make a couple comments and observations. In addition to a Whaler, I [also] have a [1996 Macgregor 26X sailboat, the] same as [the originator of this discussion]. Unlike a Whaler, these are inexpensively built vessels, and need to be modified by the owner to suit their intended use. I rigged mine to run open ocean and island hop, which it did well for many years. I'm assuming by now [the originator of this discussion has] found the electrical problem and fixed it. The advice of Jim and Jerry probably got you there with ease.

Here's my observation about Macgregor wiring: They use dime-store lamp cord. This wire will begin degrading immediately in a marine environment, and if not changed to quality wire, electrical problems will continue to plague the vessel. When you have a bit of time and a good working environment, consider changing out all the remaining lamp cord. Some of the runs are testy, so the best course is to solder new wire to the old and pull it thru. At anchor in an unsettled bay, the mast draws an arc in the sky and the wire inside slaps against the mast, whose noise radiates down inside the cabin. Very annoying. After re-wiring the mast, the wiring bundle was wrapped with four zip ties each at 3' intervals. Kind of hard to explain, but zip tie ends (untrimmed) sticking out deny the wire from ever touching the mast. It's a standoff spring I guess. Some sailors have taken to running wire thru rubber balls every few feet, but the thought of water soaked balls on the inside of an aluminum mast scares me.

The 26X is a fun affordable sailing vessel. Keep her right and have fun!

jimh posted 06-13-2010 02:34 PM ET (US)     Profile for jimh  Send Email to jimh     
We have no idea if Emilio, the originator of this discussion, has resolved his electrical problems, or if he has even read a word of the advice offered. He has never returned to the discussion he started to acknowledge any of the follow-on articles.

Thanks for the comments on how to rig a wire in a tall hollow mast to reduce the slapping noise. If Boston Whaler boats had tall masts, they'd probably be filled with foam to improve their floatation characteristics.

My experience with low-quality insulated wire is the vinyl insulation often contaminates the copper wire, resulting in a conductor that is difficult to crimp or solder. With quality marine grade wire like ANCOR now widely available and at decent prices, it makes no sense to use hardware store zip cord made in China.

64nauset posted 06-14-2010 10:29 PM ET (US)     Profile for 64nauset    
Emillio, Emillio where art thou? Right Jim, he probably changed channels and will be gone until the next glitch. I haven't been hanging around these parts all that long, but have seen a few quick in/out threads come across the screen. Not a bad thing I suppose. Folks in the boating world have found they can get cogent answers to tough questions here, Whaler or not. Good work on maintaining the high level of conversation.

“If Boston Whaler boats had tall masts, they'd probably be filled with foam to improve their flotation characteristics.”

Hehe, well I would hope no Whaler sailboat could ever heal over far enough to test that theory.

“With quality marine grade wire like ANCOR now widely available and at decent prices, it makes no sense to use hardware store zip cord made in China.”

Indeed, “expensive” Ancor-style wire is far cheaper than cheap wire. The BoatUS insurance department might agree.

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