Test for electrical leak?

[Stu Jackson]

Stephan, Charles has good advice, as does Maine Sail.

Do you have a copy of Nigel Calder's Boatowners Manual for Mechanical and Electrical Systems? If not, with a boat your size, you should. In one volume there's all you ever need to know. Charlie Wing's electrical book also gets good reviews.

You seem to need to learn about electrical systems on boats from the basics.

What MS explained are the three different grounding systems on boats: DC & AC grounds, and bonding grounds (used to tie metal underwater fittings together to avoid corrosion).

As far as colors are concerned, for DC + is red and negative is black or now yellow (a newer rule that went into effect maybe five years ago and not found on older boats like yours and mine!). DC negatives are sometimes called ground wires, since all of the negatives on the DC side are grounded back to the engine.

AC is black positive, white neutral and green ground.

If your lights are wired with black and green and they are DC, some PO used what wire he had available and didn't use the correct color code.

That's another good reason to start drawing out what you have, most of us suggest you start drawing with pencil and paper. You can figure out how to do it on a computer later. That way, you can figure out what you have first, and begin to understand it. I did that when we bought our boat in 1998- I had a basic wiring diagram from the PO, plus the owners manual which had good material. I found many inconsistencies, errors wrong info when I started tracing the wires.

As you go, LABEL the wires at each end and in the middle if need be.

It'll take some time, but they still eat elephants a bite at a time.

 

[Charles Erwin]

People

Maybe there is no stray current problem but cannot measure relative overall voltage w/reference electrode because the boat is out of the water.
Stephen reports a single zinc - mounted on the shaft. It is possible the boat is just "under zinced."
Does anybody know what Hunter 33 prescribes for its zinc inventory? One or more? If there is only the shaft mounted zinc then size/weight?

Charles

 

[Stephen Trapani]

So Stu, (thanks for the advice BTW), Maine Sail was advising me to make sure I don't have any DC grounded to the bonding ground?

 

[Stu Jackson]

Do you have a bonding ground? Most boats have Marelon thru hulls, so no need for them. Are your thru hulls metal?

 

[Stephen Trapani]

Three bronze, one marelon thru hull, I haven't looked for a bonding system for them. I know for sure two of them are not bonded.

 

[Maine Sail]

So Stu, (thanks for the advice BTW), Maine Sail was advising me to make sure I don't have any DC grounded to the bonding ground?

Actually that's not what I advised.. What I advised was that the bonding/earthing wires have no current flowing though them.

They will both, bonding/DC negative, be "grounded" at the engine but the bonding, lightning, or AC grounds are not intended to ever carry current. On your boat, assuming it is wired to standard colors (sounds like it is not), the only wires intended to carry current are the DC RED, BLACK or AC BLACK & WHITE. Bonding, lightning and AC grounding wires should not carry any current, but they often do and this can lead to corrosion issues..

 

[Charles Erwin]

Maine Sail --

From what I am reading here one runs AC safety green, radar green, battery charger green, generator green, etc. dedicated and direct to the motor block. One does not connect any green (including any through hull bonding cable) to DC ground return anywhere other than at the motor block.

In addition, where the shaft coupler insulates the motor block from the shaft, one needs to jumper the coupler to the transmission output shaft - thus to provide an electrical connection from the motor block to seawater.

Do I have this right?

Charles

 

[Maine Sail]

Maine Sail --

From what I am reading here one runs AC safety green, radar green, battery charger green, generator green, etc. dedicated and direct to the motor block. One does not connect any green (including any through hull bonding cable) to DC ground return anywhere other than at the motor block.

In addition, where the shaft coupler insulates the motor block from the shaft, one needs to jumper the coupler to the transmission output shaft - thus to provide an electrical connection from the motor block to seawater.

Do I have this right?

Charles

Yes, you've got a good grasp...

 

[LloydB]

I would rather wire all my AC green safety wires to a common safety buss and then run from it a earth ground common green safety conductor to attach at the engine separately from both the hull bonding cable and the DC negative conductor. I might install two negative conductors after MainSail clarifies the reason for the following recomendation:
" I always tend to add an extra ground wire, even on case grounded alts, that goes direct to the single point engine ground for a direct path back to the battery bank."

 

[Charles Erwin]

Lloyd -

The "dedicated" green ground buss - thence to block is a very good idea.

As to the separate alternator ground wire:

One should eliminate the motor block as an electrical conductor. The idea is that alternator ground goes direct to the battery via cable - not via the block. This separate alternator ground is added to make sure the alternator ground goes direct to the battery via cable thus by-passing the motor block.

So why are all these problems/ideas coming from the N/W US- excepting - obviously the N/E US.

Charles

 

[Maine Sail]

I would rather wire all my AC green safety wires to a common safety buss and then run from it a earth ground common green safety conductor to attach at the engine separately from both the hull bonding cable and the DC negative conductor.

Does not matter either way. None of those wires should make or create a "circuit". They are all at "earth" potential and once you bond them to the engine they are connected.. It is when people think they can just use a bonding wire to get back to the battery and connect a ring terminal to a seacock direct from the macerator neg wire and turn the bonding system into a neg return..

I might install two negative conductors after MainSail clarifies the reason for the following recomendation:
" I always tend to add an extra ground wire, even on case grounded alts, that goes direct to the single point engine ground for a direct path back to the battery bank."

I add that wire because the case grounds of starters and alternators are often very unreliable in the marine environment especially when you're trying to run 100A +/- through a rusty bracket, rusty bolts and an iron engine, which is a poor electrical conductor, compared to copper. Case grounds can be problematic and I like to "limit" the amount of current an engine block needs to carry.

I will most often use one of the starter bolts as my DC neg return and then tie the alt neg into that. This wire then runs straight back to the bank so the alt and starter are as directly connected as can be without needing to pass any current "through" the motor to get to the neg return wire.. I much prefer isolated ground alternators to case ground but when you add a good sized copper wire and copper lug to a case ground alt the current takes the path of least resistance.. My green wires also connect to the engine but do not use current carrying wires to get there.

 

[Stu Jackson]

http://www.westmarine.com/webapp/wc...catalogId=10001&page=Marine-Grounding-Systems

 

[Charles Erwin]

Mr. Jackson -

I have read these - possibly waistng the flower of my advanced years. No doubt the reference you provide shows what to do, but none of the text or diagrams show how to do it. Hence the questions.

Charles

 

[Stu Jackson]

Charles, WADR, there two ends to each wire. One identifies the wires and connects them properly. Perhaps I do not understand your questions about "how?" Maine Sail has posted some very good "How To" articles about crimps and connections. And this topic also covered connections at the engine for the proper grounds, like Reply #31 above.

What, specifically, do you need to know?

 

[Bill Roosa]

This is a taking the general concept and making a specific solution from it problem.
"I'd prefer to ......" , OK just don't break the general rules (and you didn't) and your golden. Course you HAVE to understand 5 topics very well:
V=IR
P=IV or I^2*R or V^2/R
Protect all circuits to code (right spot and right amp rating, right device)
There are 5 different types of grounds; AC, DC, lightning, radio, and corrosion prevention bonding on most boats.
and most importanly
120 volt AC (or DC for that mater) will kill you if you give it half a chance.

An oversimplification for sure but till you really understand those 5 things the rest will remain "magical electrical stuff" to you.

 

[Charles Erwin]

Stu

In this case - there are two "how" questions really :

First - if the propeller shaft is electrically isolated from the motor block and there is no bonding of the rest of the underwater metal collection - thus no other path to seawater - then how is it possible that accelerated zinc loss can be attributed to stray DC current?

Second - even if the shaft is not insulated from the motor block - how does interconnecting DC negative with AC safety green, battery charger green, etc at a location other than the motor block contribute to accelerated zinc loss - unless the rest of the underwater metal collection is bonded?

I did not intend to give anyone the impression that I was asking a wire routing question - thus wasting time. I intended only to confirm the correct wiring method in order to identify whether stray DC current could cause accelearated zinc loss where no separate bonding has been installed.

Charles

 

[Stu Jackson]

Stray current corrosion

Charles, very good questions. You had me scratching my head for awhile there, since stray current affecting zincs isn't usually the question, rather it's what stray currents can do to metals on your boat

The reality is that you're right, stray currents don't necessarily lead to accelerated zinc loss, but what could happen is that the zinc could disappear really quickly and then the metal components disappear quickly thereafter. Indeed, I wouldn't doubt that sometimes the zinc could remain while the nobler metals disappear from stray DC currents.

One of the reasons that I earlier suggested looking into the subject in books is that, for instance, Calder devotes over four pages to the subject! There really isn't a two sentence answer.

Galvanic corrosion (covered by zincs) and stray current corrosion are two separate things.

An example: "compass light switched backwards, with the switch in the negative line, current found a path to ground through the compass housing, the binnacle, the steering cable to the propeller and so back to the engine and battery negative. The rudderpost, being the part that fed the current into the water and a unbonded rudderpost, corroded until the rudder fell off!"

The issue is that stray current carry MUCH more current than galvanic currents. Most examples cited in the text are due to faulty wiring or worn insulation where the path of least resistance is to water as the ground and not back to the DC electrical system ground.

So, your question is pertinent, and it seems that stray currents do NOT necessarily accelerate the loss of zincs, which are there for galvanic corrosion issues. Rather, they set up big issues of their own.

Rather than typing the entire four+ pages, I recommend a review of Calder or other sources for those who would like to learn more about this serious subject. A lot of the examples have to do with bilge pump wiring. Guess why.

Stu

 

[Charles Erwin]

Stu -

Thank you for the reference - you can consider it read.

Just one question: This case presents with a complaint of accelerated zinc errosion and most the responses have focused on stray current as the culprit.

Do you reckon that DC stray current should attack the shaft/prop leaving the zinc that protects the shaft/prop intact? If so, then a DC stray current fault could not cause the problem at hand. So - what is the explanation for accelerated zinc errosion?

Anyway thanks to all. I mean to keep my appointment with Stephen and we will figure this out.

Charles

 

[Stu Jackson]

Stray & galvanic corrosion

Charles,

Without me doing more "homework" I just don't know, which is why I wrote my last response as I did.

Do you reckon that DC stray current should attack the shaft/prop leaving the zinc that protects the shaft/prop intact? If so, then a DC stray current fault could not cause the problem at hand. So - what is the explanation for accelearated zinc errosion?

I tend to agree with you that perhaps rapid zinc deterioration in a remote location has more to do with the quality of the zincs, as MS has mentioned, and maybe the way they were installed, than with anything going on inside or outside the boat.

This case presents with a complaint of accelerated zinc errosion and most the responses have focused on stray current as the culprit.

Maybe that's why we got off track and started mixing apples and oranges.

It could well NOT be stray current corrosion and he just has bad zincs.

It could BE stray current corrosion and the zincs are going first.

He could be sitting on top of a nuclear power plant with hot water and manatees, but I doubt it from his location.

Without that aforesaid "homework" I just don't know if stray current corrosion eats zincs first. There could be some "underwater electrical gurus" lurking here who could help. If not, it seems I'm back to "hittin' the books."

My inclination, if it was my boat, would be to treat the two issues separately. Galvanic corrosion is "treated" by zincs, when the boat's at rest and whether plugged in or not.

Stray current corrosion is a DC issue with leaks from bad insulation, wet wiring, switches on the negative and those things.

FWIW, Calder mentions that it is rare for AC to cause stray current corrosion, but, of course, the devil's in the details and the reading of the full text.

If we go back to the OP:

My evidence is mostly the very fast corrosion of zincs with no other boats around (I keep the boat on a hook). And I'm pretty sure it's DC because it's usually not hooked to AC. And when I leave the boat, the battery switch is always 'OFF.'

[and he added:] later 3 to 4 months

My records show the need for new zincs about every six months since we've owned our boat in 1998. Not plugged in, in a well wired marina. Maybe not so bad.

I look forward to your "field report." Best to Stephen.

Thanks for the insightful questions.

Best regards,

Stu

 

[MitchMan406]

Interesting read.
I have a very similar instance.

My brother just recently moved on to my Catalina 36 and has started to live aboard.
He's been running the A/C current in the boat during the last three weeks solid.

Here's the issue. I did some work on the boat: Replaced the motor mounts and aligned the mounts with the prop shaft , and now the brand new motor mounts and prop shaft/transmission coupling are all covered in light corrosion. The motor mounts shave been in there for a little of two weeks and they are almost all covered in a slight scaley powder from rust.

Very odd.
I must have some stray current from my A/C system or something.

The only thing that's really changed is the boat is plugged in all the time now with the A/C side always energized.