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Afte having spent just 3 weeks in salt water the stock anode on the 70 Yamaha is heavily crusted with a white chaulky substance; in the areas where this chaulky substance is flaked off I can see that the metal is heavily erroded. I understand that the purpose of this piece is to be sacrificial in nature and that it's depletion is entirely normal.

As I understand the situatiion, rapid depletion could be an indication of stray voltage from either my boat or from another boat near by.

Here are a few facts surrounding the situation:

1) There were no other boats in the same small harborages as I was in.

2) When I had my hands in the water I felt no electrical current from potential 120 volt leakage.

3) The first 2 weeks in salt water were in northeast and central Florida (Crescent Beach and Mosquitto Lagoon) and a small amount of pitting and mineral type deposits were noted on the anode after these two weeks.

4) The pronounced change in the metal occured during the last week while in the Florida Keys.

I'm curious about the rapid change in the metal and would like some guidance from some of you salt water boaters in this matter.

Thanks,
Zap

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Zap -

How old is the anode? Is it for fresh or salt water? There are two different kinds.

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Hey Phil,

The anode is stock and is original to the 2002 low hour, never stored in the water motor. My assumtion is that it is a freshwater anode.

Thanks,
Zap

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Fresh water anodes are magnesium while saltwater are zinc.

There is a different level of continuity in saltwater versus fresh. A magnesium anode will degrade faster in saltwater then fresh.

If you plan to be in saltwater frequently, I would get a set of zinc anodes (some motors have several anodes both inside and outside).

By the way, check the ground wires on the mid-section and near the upper pivot joint. You may have a lose or broken connection.

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Stray current doesn't just come from other boats. Marinas are notorious for stray current. A few years back, a friend of mine docked his boat at one of our local marinas and as he was tying up he noticed fizzing and bubbling from the stern of his boat. It was coming from his ground plate. The current was coming from the marina electrical system. They shut down that portion of the marina electrical system but he found somewhere else to tie up for the night.

Rapid depletion of the anode, regardless of the type, is your first indicator that something's
wrong. You can test your boat for stray current or inadequate grounding, but it's a little complicated to go into here.

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Thanks for the replys.

All the grounds appear to be secure and clean. Is the debris left behind on a magnisium anode differant than that left on a zinc anode? Mine has an off-white chaulk like substance on it.

Zap

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Every anode I've checked had a white powdery residue on the surface unless they were new. That's not the problem. What you're actually concerned with is the percent of the anode left. When they're about half gone it's time to change them out.

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Thanks to all for the help. I'll clean the anode to check for the amount left and act accordingly.

Zap

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Typically when I run my Whaler in salt water, I always have a bit of white powdery corrosion on the Cav plate and anode. Since I only run her in salt water once a year or so, I don't worry about it to much.

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Just for the record, zinc anodes are obsolete and not used any longer by the outboard manufacturers. Around 1995 Mercury stopped using zinc and switched over to more effective aluminum anodes for saltwater use. Yamaha also made the switch a few years later.

Zinc is still available on an aftermarket basis, but not recommended, and not very effective. You should buy branded aluminum anodes by your engine manufacturer. The lightweight magnesium anodes are only for fresh water use.

When an anode is 50% gone, it should be replaced.

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Thanks for all of the information guys.

From an engine protection standpoint, is it worthwhile to swapping out the aluminum anode and magnesium anode during the occassional saltwater use?

Zap

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the magnesium anode will actually offer you even more protection in saltwater, as it is even more willing to "sacrifice" itself (hence sacrificial anode), the reason that they are not used in saltwater is because they deplete much faster. For occasional saltwater use you are fine.

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Question, how does an aluminum anode protect my aluminum lower unit? Ill still with the yamaha branded zinc's for now