Electrical ground

[Greg Ross]

I've just installed a rebuilt Yanmar (3HM35) in my E-31 and have incorporated an isolator/ flex/ protector between couplings in the driveline.
Off topic-anyone in need of a reliable 2GM20F?
Where I fitted two zincs on the prop shaft the past two years for protection, and they were at least 50% consumed in 6 months service, where do I go from here? Should I provide a jumper connection to bridge the two coupling flanges or...
I have a grounding plate on the hull that has not been utilized up to this point, should this become my negative grounding point in the 12v system? And if that's correct, where should zincs be mounted?
Boat is not in the water currently (pun) but lives in a Marina where, judging by the wastage of the zincs there's perhaps some stray voltage happening.

Greg

 

[Captron]

zincs

I also used to put two zincs on the prop shaft plus the zinc on the prop itself and the shaft zincs would disintegrate in 3 or 4 months, the prop zinc a bit longer but none lasted a year.

My yard guy told me that two zincs on the shaft was the problem. Put one zinc and it will last longer. I tried that this year and sure enough one zinc on the shaft and the prop zinc lasted over 6 months.

We lost the shaft zinc when we went through a patch of weeds when it was about 6 months in the water. At that time the prop zinc was half gone and we had another month to go on our trip. When we finally got home, the prop zinc had not deteriorated any since the last inspection a month earlier.

I'm not even sure that he shaft zinc is even necessary with the prop zinc less than a foot away from it. The multiple zincs may just be eating each other.

By the way we almost never stay in marinas and when we do it's only for a few days so stray a/c is not likely the cause of our zincs dissolving.

 

[chaco]

AC/DC Grounds

Save the grounding plate for your SSB Radio
Your zincs are most likely disapearing from stray electrical current at your Dock. Your engine block is your DC ground. Create a 12V ground buss with a #2 wire connected to the block. Keep your DC ground SEPERATED from your AC ground and your Dock Electrical System will quit stealing your zincs so fast. The only connection between your AC and DC System should be your battery charger, which has an isolator on most models :nerd: Turning off your shore power at the Dock Panel when not on board will also help.
The only natural way that zincs are used up is from the current your prop shaft creates when running....thats what they are REALLY for

The Green Wire Mystery

 

[Greg Ross]

Dan,
As mentioned in my post, I've used coupling protection between flanges in the driveline so I've lost ground continuity through the proprellor shaft. Are you recommending jumpering across the isolator?
I happen to be at work just now so I'm unable to upload and post a photo link of this new arrangement. It's one of the flex/ isolators that bolts individually to the gearbox and prop shaft flanges. There's a steel band incorporated in the assembly but its' only function is to keep the shaft coupled even if the isolator is shattered with an impact.

 

[chaco]

Flexible Shaft Coupling

I have installed an R&D polyurethane Flexible Shaft Coupling with the new Beta 902. It does not break continuity with the prop shaft
If your coupling does (TEST IT !) that is a good thing for zinc life to keep stray electricty from your boat eating them up :nerd:
Zinc life is usually determined by EXTERNAL FORCES like stray AC current
in the water from your Dock Power System or other owners. Even stray DC
current from your own boat eats up zincs. Will have to look up the Test for
the current potential from the water to the boat in my Books

 

[chaco]

Corrosion Control Basics

http://www.proboat-digital.com/proboat/20070203/?pg=99
Found this Article on AC/DC Corrosion :nerd:

 

[gareth harris]

Every book I have read on boat electrical systems said the DC system should be grounded to the ocean, but none of them said why. I have never figured out the reason, until I do, or someone tells me, I can think of no reason at all to bypass the coupling.

Gareth
Freyja E35 #241 1972

 

[Howard Keiper]

I agree with Gareth...and I've had my engine / shaft and prop isolated for 10 yrs or so and have had no problems whatsoever. Whatever electrochemical action there may be is confined to the prop, shaft, and strut, and is easily controlled by a single zinc on the shaft.
Howard Keiper
Sea Quest
Berkeley

 

[Greg Ross]

I have installed an R&D polyurethane Flexible Shaft Coupling with the new Beta 902. It does not break continuity with the prop shaft
If your coupling does (TEST IT !) :nerd:

Charco,
I tested for continuity yestereday and there is none as I had assumed. Very obvious, staggered bolts from one flange to the other so there's no metel to metal path. Perhaps you should test yours?
I'll run a ground wire to the grounding plate for now.

A picture is always worth a thousand words;
http://img.villagephotos.com/p/2006-1/1138028/DSCF0124a.jpg