Hot marina "help"

[redboat42]

We have owned our 35 ft sloop for nearly 30 years. We haul every year. It is expensive but we like to keep her in as tip top shape as possible.
Three years ago we moved to a new marina. I didn't equate the problems at first but my water pump">raw water pump basically disintegrated. I bought another one as it is the only problem we have had since changing in 2010 to a D130 volvo. It has been a excellent engine and I thought raw water pump maybe a weak link??
However a year later the new pump was leaking out the cover plate and finally I realized what was going on. Electrolysis.
I put a new shore power protector on, even though I didn't think it needed it, but by the 2nd year haul out, zincs were 70% gone and some erosion on the keel was evident.I replaced hull zincs and saildrive zinc.
But then after labor day trip I was checking my engine room and sure enough the raw water pump cover is starting to leak.
I talked to the port manager about the water and he tested it noting my electrical was good but it showed I didn't have zinc protection. He noted there was a problem boat that said he had fixed electrical problems but hadn't and there were 3 other boats in my same condition because of it.
I put on scuba gear and sure enough they are almost gone. So after a little history this is my issue.

I am rewiring the entire boats ground system. copper screen throughout the bow and stern, wired both aft to buss bar, mast ,chainplates, etc etc.
We have a saildrive and since the beginning we turn off a ground break switch to kill power to the engine and it has always worked but now I am in a conundrum. If I wire it all to the engine ground it effectively takes that ground break out. If I don't wire it that way how do I have a bonded system? At some point there has to be a wire to the water doesn't there? If I have explained this well enough then how do I accomplish both isolating the engine and having a full time ground??
Hopefully someone out there has had similar problem (s)

Thankyou
Randy

[smac999]

if it's not your boat (it wasn't for 28 years) there is really nothing you can do but move.

galvanic isolators and transformers help somethings but not all.

but you should make sure it's working. this is best done with a silver silver chloride cell and somebody who knows what they are doing. (not many will) because you need to both test the working of the isolator (diode test) but also if it's being bypassed by a N-G bond or other wiring issues.

testing the isolator is easy. unplug your shore plug from the dock, and bring the cord inside the boat. near the AC panel. (with the boat end still plugged in) measure ohms from the ground on the plug to the AC ground bus on the boat. if you read 0ohms you do not have a working isolator. or it is wired wrong. if you read something higher, test it in diode mode. you should get around 0.9v. if you switch the leads around you should see this both ways. often you have to leave the meter connected for a while as it discharges and recharges the isolator in the opposide direction when you swap leads.

this tests the isolator itself but doesn't rule out other issues on the boat which may allow it to be bypassed. but testing it the above way tells you if it's in the correct spot on the ground line. vs just measuring both sides of the isolator.

everyone will have different theorys on bonding. and they all have pros and cons. reality is bonding everything is more for safety reasons and less for corrosion protection issues.

get a clamp meter that will show AC and DC amps. check the shore cords of the boats around you in both AC and DC. they should all show 0a in both if they are good. if any show AC that is scary, and the marina should be told and they should unplug it. and any show small dc (20ma-200ma) then they don't have isolators and that is somewhat normal. they are either losing zinc faster or stealing other peoples zinc depending on the current flow direction. if you see higher then 200ma then they probably have issues.

[jamhass]

It is often a single nearby boat causing the problem. Try moving to a different slip if possible.

Also, completely disconnecting from shore power can improve things significantly. Even a relatively small solar panel might (depending on you electrical usage and boat-use frequency) keep your batteries happy, it doesn't need a permanent installation either.

Finally, hanging a grounded spare zinc (I use old hull zincs) over the side can both provide some extra zinc and an early warning that your zincs are eroding. (Yeah, I know it is possible to over-zinc)

[smac999]

it's not possible to over zinc a fiberglass boat.

it is an issue with wood boats though.

[stevec195]

Easy on the diving mate! If you got the suspicion that there is stray current, remember that it only takes milliamperes to render you DEAD. A majority of marinas prohibit diving under any circumstance, and the ones that allow it have a protocol for shutting off the juice to the entire dock system prior to going in the water.


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[Sandero]

This is very troubling. Is there any way to probe the electrical state of the water around the OP's boat? If so how would this be done?

[Shrew]

Originally Posted by stevec195

Easy on the diving mate! If you got the suspicion that there is stray current, remember that it only takes milliamperes to render you DEAD. A majority of marinas prohibit diving under any circumstance, and the ones that allow it have a protocol for shutting off the juice to the entire dock system prior to going in the water.

I agree it has long been advised not to swim in marina's and boat ramps. However, I've been in many and have NEVER seen this policy in the rules. Not saying that these rules don't exist. I'm just calling 'foul' on the assertion that this is a widely adopted practice at a 'Majority' of marinas.

[landsend]

Divers in our marina routinely clean bottoms once a month on all boats. Never turn the juice off.

[ShaktisBoy]

Salt water or fresh? It makes a difference especially where diving is concerned. Fresh water will kill you quick. Much easier for stray current to pass through salt water than your body greatly reducing the risk of getting shocked.


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[stevec195]

So really now. If you truly suspected there was stray current in the water-you would hop in the drink because your marina had no policy on way or the other?


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[landsend]

That's what I pay the diver for. Seriously never really thought about it, you bring up a good point. I wouldn't get in the water for fear of catching a disease in my marina.

[Mark Stillwell]

I'm confused. The marina is aware of the issue and knows it is one boat that is causing the problem. Why isn't the marina dealing with the captain? Our marina manager would have it fixed or turn off the electricity.