Heat exchanger anodes

[pschauss]

Six weeks after launching I pulled anodes from my heat exchangers (454s) to check. They look like this. Upper one is the port engine.

http://www.ipernity.com/doc/307687/50764104

These were new just before my boat hit the water at the end of March. I have run the boat about an hour total since launching. I don't know if this is normal, but no water drained out of the raw water side of my heat exchangers when I removed the anodes.

What's going on here?

[Sheer Folly]

I think the problem is that there is a rubber wear strip on the cradle that holds the heat exchanger, preventing it from being connected to the boats bonding system.

I was going through zincs at a rate of 2 to 3 a year on my 1988 454’s.

Last year for my Winter layup (in the water) I soldered a male spade connector to the brass nut of the zinc and ran a female spade connector and wire to my boat’s bonding system.

I don’t know how well it works because I haven’t checked yet because I haven’t recommissioned my engines, but will before this weekend.

I’ll let you know how it works after that.

[Yannis]

Why do I think it’s the other way around?

When something is isolated or not bonded, then the zincs are not consumed.
This seems like there is some stray current somewhere, either on the boat or in the water around the boat.

[MarkD]

Try sticking a screwdriver into the hole and break the old zinc debris free and the water will come out. I often have this on my gas engines.

[pschauss]

It’s not a bonding issue. I have continuity between the brass plug and the block.

The odd thing is that the zinc is eroding next to the plug and not at the far end.

[Yannis]

Not only that, it is that it is eroding super fast too.

[Amberjack]

Peter, this is highly unusual anode deterioration. Normally they degrade uniformly along the whole zinc and there is some of that evident on yours. The severe zinc loss at the plug end indicates to me a stray electrical current in your engine block. This is my best guess. Someone out there has seen this before and should be able to diagnose it immediately by looking at your pictures.

[Stephan]

Did you flush you cooling system with acid after installing the zincs?
I know that will east them up quickly.
Good luck,
Stephan

[mike ohlstein]

DISCONNECT your shore power cord!!! Like NOW.

Then get a guy with a proper meter who knows how to use it.

[Stephan]

Do you have zincs in your transmission/oil cooler as well?
Stephan

[Marshall Mahoney]

Or stray DC current. I have been fighting it for years -- with improvement but not solved. I open my selector switches at the end of each trip. This is one of the better articles I have found: https://sites.google.com/site/catalaocm ... -corrosion. If your voltage leak is significant, you may be able to perform a quick check. Disconnect shore power, bilge pumps and open circuit breakers/selector switches. Disconnect negative battery terminal and place a dc multi meter between the cable and terminal (should read 0 volts ). Check voltage as you close selector switch, shore power, and circuit breakers. Usual suspects are bilge pumps and battery cables with failed insulation laying in the bilge. Also, neighbors wiring problems trickling in thru the shore power ground wire (galvanic isolator needed). If you are only seeing corrosion on your engine anodes and not running gear anodes, concentrate your efforts there. If nothing is found, invest in a reference anode and painstakingly work thru each circuit.

[Tony Meola]

Once the shore power cord is disconnected, you can then determine if it is the DC or AC side. If the problem ooerdists yyhen you gasve aleak on the 12 volt side.

To find the issue on the 12 bolt side you need an Ohm meter. You have to turn off every DC device on the boat. Then disconnect the batter cables. Hook the ohm meter to the positive and negative battery cables. Then sts then pick a device and turn it on. You should have an Ohm reading as a functioning device will show ohm resistance. If you are showing ohm resistance, then turn off the device and pick the next one to turn on. Keep doing that until you find the device that has a 0 ohm reading. That is your bad 12 bvolt device.

On our boat it was the rear binge pump. Ate the zinc off g ghe shafts and funders in 2 weeks.

[Stephan]

Tony-
I had a similar experience with a Rule bilge pump float switch.
In a matter of days the zincs looked singed. Then I replaced the float switch and was good for the season.
Stephan

[pschauss]

Why wouldn’t a short in the float switch blow the fuse?

I just finished replacing my aft bilge pump because it kept blowing the in-line fuse. Both of my bilge pumps have an in-line fuse at the battery connection.

[Carl]

Leaking juice from a switch, connection I am "guessing" is enough to make a meal out of your zincs and metals in contact with water but not enough of a leak to be an actual short that blows a fuse.

[Tooeez]

If it's any kind of electrical issue all the zincs on the boat should be wearing rapidly also, so it might be a good idea to check the running gear. As for the odd wear pattern, if the exchanger is draining at rest then there might only be a 1/2 inch or so of water around the zinc most of the time--and if the anode isn't in the water it can't erode.