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post #11 of 24 Old 07-21-2016 Thread Starter
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Re: 12V ground on the boat

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I (for one) am not sure that's true. Most RWC engines have their own anodes (usually pencil anodes) installed in the cooling system someplace for this purpose.

Anyways, Volvo produce very good clear and concise diagrams and instructions on how to properly connect, maintain and operate their engines.. you better check the manual.


EDIT: FWIW, to help protect the engine from internal corrosion my FWC Volvo MD2040 is fitted with an "earthing relay" specifically intended to ensure the engine is not earthed to anything other than the battery under normal conditions.. but I realise your engine may be different.
I have the service manual for the MD6A, which apparently differs from the MD6B only in relation to the starter/alternator configuration, and the user manual. There is no mention of sacrificial anodes on the engine. I am necessarily nowhere near certain that my diagnosis is correct, however visual inspection of the sail-drive (and literature) suggests that it and the prop is insulated from the sail-drive housing. There is a sacrificial anode associated with the sail-drive, and mine is rather spongy and weak; I will not be able to replace it before the fall at the earliest.

My reading so far indicates that this subject is rather complex. Considering the age of this boat and that it is in rather good condition for that, it seems prudent to leave well-enough alone at this juncture. My laundry-list for the boat and motor is long enough as it is and I must prioritize.

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post #12 of 24 Old 07-21-2016
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Re: 12V ground on the boat

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Originally Posted by Frogc View Post
My reading so far indicates that this subject is rather complex. Considering the age of this boat and that it is in rather good condition for that, it seems prudent to leave well-enough alone at this juncture. My laundry-list for the boat and motor is long enough as it is and I must prioritize.
I'd agree with that.

Generally, if an engine is insulated from the prop, it's not intended to be earthed to anything other than the battery -ve. The manuals are usually pretty specific on how the engines should and shouldn't be connected (I know the manual for my engine is). I always go with what the manual says and, if in doubt, leave well enough alone.

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post #13 of 24 Old 07-22-2016 Thread Starter
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Re: 12V ground on the boat

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I'd agree with that.

Generally, if an engine is insulated from the prop, it's not intended to be earthed to anything other than the battery -ve. The manuals are usually pretty specific on how the engines should and shouldn't be connected (I know the manual for my engine is). I always go with what the manual says and, if in doubt, leave well enough alone.
That's actually pretty funny; I can leave well enough alone either way!

In any case I am not done with this issue and will revisit it as old information leaks out of my brain, freeing up space for new information.

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post #14 of 24 Old 07-22-2016
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Re: 12V ground on the boat

disconnecting the battery +ve terminal will tell you if the 30 Mv come from loss of insulation anywhere on the +ve side , unless you starter has two wires the block maybe already connected to battery negative.
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post #15 of 24 Old 07-22-2016
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Re: 12V ground on the boat

Rebuild it man.
Get a shop to replace the board stolen by neptune.
Clean up the upside face of the hatch use 40 grit sander or grinder with a light touch. Wash it with solvent acetone or similar.
Score the underside of the boards with a craft knife then wash then in acetone also.
Coat the upside face of the hatch with a 1/8 layer of epoxy glue also the underface of the boards.
Bed the boards all back into place making sure the push into the epoxy. If not lift out and apply a bit more.Try to get all the gaps about the same.
Any excess which oozes into the gaps must be cleaned out with a nail or similar before cure.
Dont worry about the surface being flush too much as you will sand to achieve this but get as much board in as you can.
When cured after 24 hours tape the boards & perimeters edges and apply a premium calking mastic.
When all set cured ( best to leave a week ) Sand and appy finish or your choice .
Enjoy your foray into resortaion
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post #16 of 24 Old 07-22-2016
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Re: 12V ground on the boat

What amazed me was that most of the boats with grounding anodes on the exterior of the hull, including my own when I first purchased it, had several layers of bottom paint covering the anode, thus making it worthless. I spent an hour scraping and grinding the bottom paint from my boat's anode and it is now functional and connected to the base of the mast with a length of 2 gauge wire. This connection is also used for my SSB radio ground, which is recommended in the radios user manual.

As for having a wire running to the boat's keel bolts, there will not be much in the way of grounding with an earthen ground if the lead keel is fiberglassed over and painted. Doesn't make a lot of sense to me using this kind of setup. And, what if the keel is made of poured concrete? That sucks!

The only ground system to true earthen ground that makes any sense at all is the engine and prop shaft, both of which will likely have sufficient bare metal to provide continuity.

Now. whether or not that ground anode will protect me from a lightning strike to the mast has yet to be tested, though the PO claims that's why he had it installed. I'm really not sure if anything will protect your boat or electronics if lightning nails the top of your mast.

Good luck,

Gary
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Re: 12V ground on the boat

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Originally Posted by travlin-easy View Post
What amazed me was that most of the boats with grounding anodes on the exterior of the hull, including my own when I first purchased it, had several layers of bottom paint covering the anode, thus making it worthless. I spent an hour scraping and grinding the bottom paint from my boat's anode and it is now functional and connected to the base of the mast with a length of 2 gauge wire. This connection is also used for my SSB radio ground, which is recommended in the radios user manual.

As for having a wire running to the boat's keel bolts, there will not be much in the way of grounding with an earthen ground if the lead keel is fiberglassed over and painted. Doesn't make a lot of sense to me using this kind of setup. And, what if the keel is made of poured concrete? That sucks!

The only ground system to true earthen ground that makes any sense at all is the engine and prop shaft, both of which will likely have sufficient bare metal to provide continuity.

Now. whether or not that ground anode will protect me from a lightning strike to the mast has yet to be tested, though the PO claims that's why he had it installed. I'm really not sure if anything will protect your boat or electronics if lightning nails the top of your mast.

Good luck,

Gary
and then there is the theory that the lightning will seek out the boat with the best mast grounding system
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post #18 of 24 Old 07-22-2016
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Re: 12V ground on the boat

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Now. whether or not that ground anode will protect me from a lightning strike to the mast has yet to be tested
Nope. We call those wires "fuses."
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post #19 of 24 Old 07-22-2016
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Re: 12V ground on the boat

Marine Grounding Systems | West Marine

Stu Jackson, Catalina 34, 1986, M25 engine, Rocna 10 (22#), Maple Bay, BC, Canada
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Re: 12V ground on the boat

Since you found an old zinc strap ,I think it is supposed to be grounded thru the hull electrically (keel bolts or thru bolt to bonding wire/strap/.No guarantee the shaft/prop is in the system unless shaft is grounded .The coupling may isolate. Needs a brush on a grounding wire. Possible to over zinc and add to problems. None of this is a cure for lightning.
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battery , earth ground , electrical , ground , lightning

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