Help understanding mercathode

[Coz]

I have an 08 310da. Schematics show mercathode system but I can’t find it anywhere. Don’t see a controller in engine compartment or anything on the transom that looks like anodes, certainly nothing with wires going to it.

Were these not standard equipment?
Would it help with keeping the drives clean? I was in the water 3 days and had hard crusty bumps all over my drives and white film that won’t come off.

 

[BillK2632]

Certain yours has it - standard on all BIII models. The controller is a box mounted on the rear of the engine - Mercathode is clearly labeled on it. The electrode is mounted on the front of the drive, looks like an anode. The Mercathode helps control corrosion, it won't do anything to keep the drive clean.

 

[Lazy Daze]

Have you had the boat since new? It should be there. If you bought the boat used... who knows what a previous owner may have done - sometimes their decisions don't seem to make a lot of sense.

As mentioned, it helps to keep corrosion at bay, not to stop growth. Anti-fouling paint helps with growth.

Not sure where you are boating, but a product like On & Off should help with the crusty growth. Read the label, though.

 

[Coz]

I found a cable near the trim cables behind the engine labeled mercathode. It runs down low on transom and I can’t see where it goes. The other end plugs into a harness on the engine. Don’t see a controller.

Do the wires go through the transom or is it just those bare steel cables jumpering across metal parts?

 

[Coz]

I see the mercathode electrode right below where the hydraulic lines are for the trim cylinders. nothing that looks like a zinc but it does look like what I see online.

 

[paulswagelock]

Find your controller mounted on the rear of the engine up top. Likely blue plastic. Look up a picture online so you know what to look for. Then check the leads to verify it is functioning.

 

[dlvwill]

Find your controller mounted on the rear of the engine up top. Likely blue plastic. Look up a picture online so you know what to look for. Then check the leads to verify it is functioning.

The controller might be up front next to the oil filter.

 

[Coz]

Found it right behind the drive oil reservoir.

When I bought the boat last fall the stainless steel hydraulic lines had a lot of corrosion on them. Is that normal in fresh water if mercathode is working properly?

 

[paulswagelock]

My last boat with a b3 drive was in fresh water for 7 years while I owned it for the summer seasons. The drive and stainless hoses looked brand new after 7 years.
Make sure the anodes are correct metallurgy and test the operation of your mecathode system.

 

[Lazy Daze]

You shouldn't really have 'corrosion'... but they could be brown and stained with stuff growing on them. Got a pic?

 

[Coz]

I guess it’s not corrosion, there’s no loss of material. They were covered in what looked like dried mud, but the stuff was super hard and only on the stainless steel. I’ve gotten most of it off now except around those bonding cables.

Guess I need to figure out how to test them.

 

[Coz]

There’s nothing to replace on the anode is there? I mean nothing that depletes over time.

 

[Lazy Daze]

I guess it’s not corrosion, there’s no loss of material. They were covered in what looked like dried mud, but the stuff was super hard and only on the stainless steel. I’ve gotten most of it off now except around those bonding cables.

That's exactly what I was thinking was actually going on. That's just lake scum that has dried on. Removing it right when you get out of the water is easier. But it's nothing that Slimy Grimy or On & Off can't easily take care of. Those two products will basically just melt it right off before your eyes. Just cover the trailer as they can stain galvanized or aluminum trailers.

 

[Lazy Daze]

There’s nothing to replace on the anode is there? I mean nothing that depletes over time.

What anode? Are you referring to the Mercathode? No, nothing wears away. It either works or it doesn't.

 

[JimT]

What anode? Are you referring to the Mercathode? No, nothing wears away. It either works or it doesn't.

I thought the Mercathode system could function sometimes at reduced levels hence the need to check it periodically. Is that not correct?

 

[paulswagelock]

The controller can go bad. It needs tested periodically.

 

[Lazy Daze]

I thought the Mercathode system could function sometimes at reduced levels hence the need to check it periodically. Is that not correct?

Not that I'm an expert on this subject, but I'm not aware of it functioning at various levels. I don't think it's that smart

 

[paulswagelock]

Here are some quick troubleshooting things you can check:

Check mercathode power on two center screws for 12 volts DC

When the boat is in the water, disconnect the orange wire that comes from the anode at the mercathode controller. Set the digital meter to show milliamps. Connect the black meter lead to the terminal on the controller. Connect the red meter lead to the end of orange wire. If using the blue or black Mercathode controller, the reading should be 25 or less milliamps in freshwater, to as much as 200 milliamps in saltwater areas. If using the red Mercathode controller, the readings should be less than 25 milliamps in fresh water areas to as high as 400 milliamps in saltwater areas.

 

[JimT]

Not that I'm an expert on this subject, but I'm not aware of it functioning at various levels. I don't think it's that smart

On my prior boat a 280DA I was getting galvanic corrosion on the drives due to what I assumed was stray current in the water. I had the mercathode tested and it was on the border which Paul says is 25 milliamps. I thought about upgrading to the high capacity red mercathode system but ended up changing marinas which solved the problem.

 

[Lazy Daze]

I think we may have been thinking of different "levels" in different ways. I was thinking in terms of the boat being in the same water and the module turning up the juice or down the juice throughout the day.