Mercathode Gone Bad - Real Bad

[Stray Cat]

First let me say my experience here is in fresh water ( Mississippi River) if you're in salt water, your experience may differ.

As part of my annual replacement of drive annodes for my B3's, I take a little extra time to make certain both of my Mercathode Reference Electrodes are in shape for another season. My boat is wet slipped, so finding some scrunge around the electrode (wire that looks like a paper clip) is normal. But, the electrode should be exposed enough that it is exposed to the water.

The reference electrode on my B3's are fastened to the bottom of the distribution manifold for the hydraulic lines for the trim/tilt cylinders. I normally use a soft bristle brush to knock away the scrunge that accumulates. Upon inspection of the stbd side drive, I noted the "wire" was seperated where it comes out of the center of the housing. (see where the pencil is pointing) The wire's normal shape represents an oval (like a race track) , however the wire doesn't rejoin where it comes out of the center of the housing. This one will not give you one bit of protection and needs to be replaced.

Last year I replaced the one on the port drive. I've had this style of reference electrode (there is a puck style too) on two different boats, 270DA & 300DA, I seem to get around 4 yrs of service before they need to be replaced....

I hope some of you find this helpful. I can say from experience, these things make a big difference in keeping corrosion at bay...as long as you are not slipped in a fast current.

btw - sorry I didn't have the new one to compare it to, it is now under water

 

[Dave S]

Some folks paint those when repainting their drives. That renders them ineffective as well.:smt021 Other folks aren't even aware it exists at all and think the only thing they need to worry about are the anodes themselves.

 

[Stray Cat]

Dave, have you ever used one of the reference electrode testers like the one offered at Boat Zincs.com? Mercury makes, or at least used to, a push button tester that connects to the controller. Dunking the probe would atleast give a meter reading as to their effectivness...

 

[Dave S]

I contemplated buying one but decided against it until my warranty is up in 2012 because even when you detect a problem you have to solve the cause of it.

I pull my boat and look at my drives at least every six months and that is really a measure of how well everything is working. By now I know what to expect (in the way of corrosion issues) and if something is out of the ordinary I tell the dealer to start looking at the issue. I have a good working relationship with my dealer and they know I won't BS them so that helps too. They also know that I regularly repaint my drives as needed and change my anodes. I also keep digital pictures of the drive each time I have the boat out of the water as well.

Dave

 

[JohnEGraham]

Hey, Stary cat; Are we looking at the exposed part or is that what we see if we take it apart.

 

[Stray Cat]

John - What you see in the picture is the electrode that is exposed to the water. There is no taking it apart. If you were to flip it over, there are two insulated wires that are molded into the body that are routed up through the drive to the controller. The controller is generally mounted to the transom inside the engine room.

Here is an exploded view of the controller & the electrode

 

[JohnEGraham]

Cool! thaks for the pic. I will have to trace it out on my boat. I have seen the top part, Controller under the galley. JG

 

[SCORPIO]

How is that wiring routed and sealed going into the boat? I have some new Mercathodes I'd like to install but haven't looked to see how to run the wires into the boat. Hope its easier than the trim limit switches.

 

[Stray Cat]

This is how I do it for a Bravo 3....not certain if an Alpha is similar.

The reference electrode comes with the male connector fastened to the end. I find it impossible to fish it through the hole into the boat. When removing the old unit, I try to get some extra wiring to pull down from inside of the boat. Then I cut the old electrode's wiring off real close to the housing. Next I cut the male connector off the new electrode leaving about 4 inches or so of cable attached to it. Then I strip the wires and twist and tape them together so I can pull the new cable into the boat using the old cable to pull on. Once I get it in the boat, I reattach the electrode with the two bolts, then use heat shrink butt splices to reconnect the male connector to the cable.

I found that when the factory installs the electrode, they use tie straps and pull them pretty tight to secure the cable against the transom. I had to clip the straps to allow the old cable to be pulled down enough to strip the wires and attach them to the new cable.

 

[SCORPIO]

If I read that correctly, the splice ends up inside the boat right? If thats right, then I think it would work fine.

 

[Stray Cat]

If I read that correctly, the splice ends up inside the boat right? If thats right, then I think it would work fine.

Yes, inside of the motor compartment.

 

[Walz]

THANKS so much for posting the picture! I have been cleaning what I thought was a functioning Mercathode for the past two years I have had the boat, but now it seems all I've been doing is cleaning plastic as the electrode is completely gone!! I doubt that the electrode has ever been replaced. I have two new ones on order and will install before the boat goes back in the water this season.

 

[Stray Cat]

Glad to help Walz....if you want to learn more, below is a link to some good toilet reading (well, print it first) or you can request Mercury's 90-881813 01 bulliten titled Marine Corrosion Protection Guide, a wealth of info on the mercathode system with good pictures showing greater detail. A few years ago some of the members here contacted Mercury and they sent the mentioned bulliten at no charge.

http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Race-Sterndrives/2002/EN_05.PDF

 

[JohnEGraham]

Hi, Can the Electrode be replaced or does the unit have to be changed. The wire cable is very tight and not sure I can even get the the inside.

 

[JohnEGraham]

looking at mine I don't see the wires hooked up to the Paper clip. ( small piece left) Are there diffrent models this is 98869a17?
Thanks

 

[Stray Cat]

John - The whole unit has to be replaced. I found your pic from the link below, I saved it to my desktop so I could zoom on it. From that view, I could see where the wire runs under the grey colored insulator and forms the paper clip. Mine always have looked that way.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=120345354866&viewitem=

You may need to go in your motor compartment and find where the wires fish through the transom. I remember the 1st time I replaced mine, the factory cut the wires so short that there wasn't any slack in the engine room to feed down to pull the housing away from its mount. I ended up cutting the old wires off real close at the electrode, pulling the old wires into the ER, and then used a flexible wire to fish down through the hole so I could pull the new wires.

 

[JohnEGraham]

Okay, So there are no wires shown in your Original picture ( with your the Broken wire) and the wires we see in the "ebay" pic? Is this an up-grade from the original Mercathode?
I had to pull hard on the wires to get the unit down that far to look at the back, I hope I did not pull the wires apart. ):
Thanks John G.

 

[Stray Cat]

To my knowledge, they havn't changed them. My first experience with it was on a 99 270DA I'm pretty sure they are the same today, but not 100% There are no wire leads shown on mine because I had already cut them off close to the housing to remove it from the boat.

If your unit was factory installed, they normally don't give you much extra wire. Even after unplugging it from the controller, there are tie straps holding the wire leads out of harms way. After the tie straps are cut and it is disconnected from the controller, it pulls down fairly easy. The wires on the back of the unit are molded into the plastic with a unique looking rubber seal used (it is molded into the plastic housing too) to keep the water out of it.

Keep at it, you'll get it. Doing it the first time is the most difficult.

 

[SCORPIO]

How is the wire entry point to the boat sealed? What keeps it in the sealed hole?

 

[Stray Cat]

How is the wire entry point to the boat sealed? What keeps it in the sealed hole?

There is a molded interface seal on the flush side of the electrode housing that is sandwiched to the flat hydraulic distribution manifold (for the tilt cylinders) by two hex head bolts. It is a reliable seal, I've never had one leak...yet.