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Ric66

stray electric current

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I am toying with the idea of buying another bigger boat and keeping it at a marina. I've always had aluminum boats but am concerned that if I leave an aluminum boat at a marina that stray current from other boats/docks could affect my boat. Does anybody keep an aluminum boat at a marina? Should this be something I concern myself with?

Thanks for any feedback.

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The zinc anodes on the aluminum boat/outboard/outdrive are placed on them as a protection against this.

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Stray current is a concern with slipped boats, no matter the hull material. Make sure your sacrificial anodes are up to the task in not only life span, but also the right kind. Most drives come with zinc, but I have researched and found that magnesium anodes are better in freshwater. You can also hang anodes over the edge of the dock to aid in warding off electrolysis of your drive or hull. Take a look around your marina too. If you see wires in the water or on the docks that look worn, or unkempt, address it. If there are boats near you that are plugged into shore power, be aware they may be leaking current too. Some do, some are just fine. Good luck and inspect your drive often. I had a Bravo 3 drive go bad due to electrolysis(and age).

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Don’t think so. Never heard of that being an issue.


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10 minutes ago, guffins fisherman said:

Stray current is a concern with slipped boats, no matter the hull material. Make sure your sacrificial anodes are up to the task in not only life span, but also the right kind. Most drives come with zinc, but I have researched and found that magnesium anodes are better in freshwater. You can also hang anodes over the edge of the dock to aid in warding off electrolysis of your drive or hull. Take a look around your marina too. If you see wires in the water or on the docks that look worn, or unkempt, address it. If there are boats near you that are plugged into shore power, be aware they may be leaking current too. Some do, some are just fine. Good luck and inspect your drive often. I had a Bravo 3 drive go bad due to electrolysis(and age).

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Electrolysis is a very real & common issue for all the above reasons & precautions that Guffins listed above.  I see signs of it on just about every boat that's slipped for the season especially where shore power is in use. Be aware of it & keep an eye on your zinks/magnesium anodes for any signs and you should have no problems. 

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It seems not much people know that zinc anodes are not of much value in fresh water. They are recommended for salt water. Aluminum anodes are a bit better in fresh water but are recommended for brackish water. Magnesium anodes are best for fresh water issues. They are available for most out drives and outboards.

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So is the anode on the motor also protection for the boat? Can't say I've ever seen an anode on the boat. should I be leaving my lower unit in the water I've always tipped my motors so they didn't grow fur.

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Switched my bravo drive on a 26 wellcraft to magnesium anodes and couldn't believe how eaten up they got in one season. That's a GOOD thing. Bottom line, if your zincs still look like new, they're not doing much for you! They're called sacrificial for a reason.

 

My source: https://www.boatzincs.com/

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12 hours ago, lrg355 said:

It seems not much people know that zinc anodes are not of much value in fresh water. They are recommended for salt water. Aluminum anodes are a bit better in fresh water but are recommended for brackish water. Magnesium anodes are best for fresh water issues. They are available for most out drives and outboards.

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I've read this also. Can you get them some place around Rochester or do you have to order online?

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10 hours ago, horsehunter said:

So is the anode on the motor also protection for the boat? Can't say I've ever seen an anode on the boat. should I be leaving my lower unit in the water I've always tipped my motors so they didn't grow fur.

I also wondered about this. Aren't you inviting zebra muscles by keeping the motor in the water?

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There are usually a single or more anodes mounted on the out drive or outboard motor transom bracket that will be under water even when the motor or drive itself is trimmed fully and out of the water and much as possible. If you buy a full magnesium kit they will be included.

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11 hours ago, lrg355 said:

There are usually a single or more anodes mounted on the out drive or outboard motor transom bracket that will be under water even when the motor or drive itself is trimmed fully and out of the water and much as possible. If you buy a full magnesium kit they will be included.

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Thank you for the info.

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The sacrificial anodes are a "softer metal " that the stray current attacks first. On inboards you will find them on prop shafts , rudders ,and trim tabs. Also inboards will have a bonding system that is basically heavy duty wiring attached in a series to every metal part that goes through the hull and makes contact with the water , including through hull water intakes if they are bronze. The purpose is to spread out the damage that can be done by electrolysis eating away at the weakest /softest metal that is exposed. By doing this it basically makes them all the "same " when being zapped. So it spreads out the damage ,hopefully making it all minimal ,instead of say the prop shaft  taking all the brunt . Generally you can get two years out of them in this area because of the shortened season , depending on where you keep slip your boat . If in a marina with a lot of boats plugged in it's going to be every year. I believe they go more by weight more than appearance when declaring them no good.

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Was told at the marina yesterday that they have purchased some sort of probe that they can walk the docks every morning and determine if any boats are leaking any stray current.

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13 minutes ago, horsehunter said:

Was told at the marina yesterday that they have purchased some sort of probe that they can walk the docks every morning and determine if any boats are leaking any stray current.

Which marina was that?

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Electrolysis has nothing to do with the "softness" or "weakness" of metals but is totally controlled by how Noble a metal is. This is the term used to define its resistance to corrosion (oxidation). Gold is a very soft and mechanically very "weak" metal but is very noble. It can lay on a sunken ship in the ocean for a thousand years and look like new. Magnesium is one of the least noble metals and oxidizes very easily. In fact, a thin strip of magnesium will flash burn when subjected to a flame, ie rapid oxidation. Aluminum is of low nobility so you need something lower to corrode faster, ie Magnesium. Brass has a generally high nobility and stainless steel, depending on the type, Is very high.

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