Checking Merc Anode System

Capt Ron

I noticed that my Merc B3 drives are starting to corrode.. I just changed the anodes last year and they are still in good condition... I'm concerned the Merc Anode system may not be working properly or not at all... is there a test I can perform to determine if it is working ok.

MarkB

Good question, I'd like to know that as well. Not that my drives are corroding, but as preventative maintenance.

However, are your anodes making good contact with the native metal?  No paint in the way?

Black_Diamond

You need a reference anode and a volt meter. The reference anode can be got here:

http://www.farwestcorrosion.com/marine-galvanic-isolators-gi-by-dei-marine.html

You can not only check the Mercathode but ALSO hunt around your dock/marina for boats with stray current. 

Pretty straight forward to use. I have one plus a jumbo anode I can put in the water too, just connects to your battery (-) terminal. 

Cableguy Greg

Here is the reference anode that I have...

http://www.boatzincs.com/corrosion-reference-electrode-specs.html

@Black_Diamond , how well does the jumbo anode work? I bought one to use this season. I am going to store it in my rear hatch while underway.

Black_Diamond

I think it works, I use it when at transient slips.  I ran a ground wire from the ground block into the rear hatch area on my 342 so it is a quick clamp onto the wire.  Cheap insurance!

Black_Diamond

The reference anode I have is the same as the one in the link Cableguy has.

Michael T

It is almost impossible to get a good reading on the Mercathode system's function (direct quote from mercury) even when using their reference tester. I have tried with friends and techs. mercury said (over a number of conversations I had with them) if there is ANY wind or water current the test is essentially meaningless. Don't take my word, call them yourself... for a frustrating conversation -  LOL

So I asked Mercury what the h*ll are we supposed to do. Their answer: check the wiring on the system for continuity - as defined by - make sure the SS wires are all connected and in good shape. Check the black box under the drive at the transom has not been damaged and their best suggestion: make sure you have a galvanic isolater (Rinkers do) shore power cables that are in good condition and mercury's number one suggestion - make sure you are using the correct anodes in good or better condition.

One tech did say he had developed a way with a meter to see if there was a an electrical draw on the batteries from the system but he too said using the reference anodes stc. in the water was IHO a waste of time.

My bottom line - check the condition of the wiring and your anodes. Don't use crappy shore power cords.

Black_Diamond

I can see current messing it up. I was able to get very good readings on mine actually. 

Capt Ron

Thanks Mates all good points.. I also found out not to mix anodes on the drive and trim tabs... make sure they are the same material... I changed all my anodes from AL to MG including the trim tabs as well... hopefully it will fix things... let you know..

Michael T

I believe going to magnesium will make a big difference.