Part of Mercathode?

[djred889]

Went to check on our boat this past week after all the snow we had and to get an idea of what has to be done this spring. I know we've got a lot of work getting the drives ready for the season but I can't figure out what the round things attached to the transom are. They are on the left and right of each transom assembly. They have a metal plate in them. My guess is that they are anodes for the mercathode system? If they are, do they have to be replaced just like the anodes on the sterndrives?

 

[Don S]

Re: Part of Mercathode?

My guess is that they are anodes for the mercathode system? If they are, do they have to be replaced just like the anodes on the sterndrives?

Yes, they are part of the Mercathode System. No, they do not get replaced like anodes.

I do see a corrosion problem around the Mercathodes and the drain plug. You should really get the system checked out, the procedures are in the OEM service manual. It may be that those large anodes between the mercathods are just too much for the system and causing the corrosion.

 

[djred889]

Re: Part of Mercathode?

I believe the large metal plates in the center are the ground bar for the boats electrical system and can't be removed. I understand that the anodes on the sterndrives are designed to take the corrosion and not the drive itself, but I don't understand what the anodes on the transom are for. Besides testing the systems, is there anything else I should do?

 

[Don S]

Re: Part of Mercathode?

I can only go by what I see in a single picture. So it could be a ground plate, but I doubt it. Looks more like the A30 plate zinc.

http://www.go2marine.com/product.do?no=42048F


If they are anodes, between them and the anodes on your drive would be enough in most cases, but to add the Mercathode system into the mix also, usully means the hull and outdrive are protecting your zincs. That is why you need to do the tests.
Here's the manual for your drive, look at section 7 for the testing procedures and what to do with your readings.

http://www.4shared.com/document/7ctpcLpn/Service_Manual_28r.html

 

[djred889]

Re: Part of Mercathode?

We will have the system tested next month when we start working on it for the season. If the zincs are in fact anodes and not grounding plates, should they be replaced? Also, our boat is in a slip all season in brackish water and occasionally we take it in salt water. I was told that aluminum anodes should be used for that type of water? I'm not sure what type of anodes are currently on the drives as the boat is new to us.

Here is another picture, not sure if it will help.

 

[djred889]

Re: Part of Mercathode?

I just checked the parts manual for our boat and they are in fact M-30 hull anodes.

 

[Don S]

Re: Part of Mercathode?

You should have aluminum anodes, not zinc. If it was my boat, and the paint looked like it does on your transom, the 2 center plate anoses would be removed for not. Then new OEM aluminum anodes installed on the outdrives. Do the checks that can be done on the Mercathode system while the boat is out of the water. Once back in the water, do the tests, and fill out the worksheet shown in the service bulletin I am posting links to. .
At the price of new drives, you really need to make sure they are protected properly.

http://www.4shared.com/document/ViLRp-nH/02-06_Corrosion_Prevention_and.html

Also, have a look at these other bulletins on anode materials.

http://www.4shared.com/document/48EUSOEi/03-02_Aftermarket_anodes.html

http://www.boatfix.com/merc/Bullet/91/91_19.pdf

 

[djred889]

Re: Part of Mercathode?

Don, thanks for the help. I will be sure to replace the drive anodes with OEM ones and perform all the checks on the Mercathode systems. To be clear, you recommend removing the hull anodes instead of just replacing them? The rational being that they are overkill considering we have the Mercathode system. I am also going to touch up the bottom paint where the corrosion has occurred.