Mercathode antifouling ?

[DIY1111]

Have had same engine for 15 years. Mercathodes a pita. Not sure they even function... my question - is it possible to use an anti fouling paint on the housing of this without a negative affect - Obviously, not painting ‘the wire’ or near it. Mine gets fouled up pretty badly each season...

 

[alldodge]

Not sure what fouled up means, but if it means the anodes and eaten then need to measure the field.

Need a good voltmeter and a platinum probe wire

Fresh Water Areas -
620 - 1180 Millivolts with Digital Meter
Salt, Polluted or Mineral Laden Water Areas:
750 - 1180 Millivolts with Digital Meter

 

[DIY1111]

Mercathode under transom mount - it gets heavy barnacle growth. I’d like to paint the plastic housing, not the electrode wire with either a transducer paint or trilux. Want to make sure that I want be negating the mercathodes affect...

 

[alldodge]

I would say no, but just my opinion
As you said the unit is plastic, so painting it I don't see it doing any good, or even sticking
Another issue, is there should be 3/4 to 1 inch space where the bottom paint does not touch the transom. If the paint does touch, then the copper or other metal in the paint makes things worst

 

[DIY1111]

Plastic not an issue - paint will stick. I have the 1” no paint zone around transom mount - need someone who knows If painting mercathode is a detriment to its function...

 

[achris]

... - need someone who knows If painting mercathode is a detriment to its function...

Yes. DO NOT paint.

BTW, Mercathode is to reduce galvanic corrosion, not fouling. You still need to paint the drive and the hull to reduce fouling. But DO NOT paint the Mercathode at all! That will 100% stop it working.

Chris......

 

[DIY1111]

Chris. Thx. Totally know what it does although I do think that its an odd mechanism. Other than going to a mercruiser dealer to use an in-water, probe to see if it's actually doing its thing - you never really know. And, even that process is suspect due to all the the variables; loose marina electricity, other noble metals in the water etc... Wish you could could just touch the under transom mount exposed wire to a volt meter while on the hard and measure its effect.

OK - so no paint for this thing ! Mine gets really fouled with barnacles. And you can't clean it properly due to the aforementioned wire. Even on dry dock, cleaning it is a fragile event ( think - dental tools. ! ). All other underwater metal and fittings pretty much painted to avoid this issue - but the good 'ole mercathode is a barnacle's dream ! If it were a $30 part - no harm.. no foul, but it isn't. Was hoping I could use transducer anti-fouling on it at the least. Oh well...

 

[alldodge]

You can replace the wire with these
https://www.mercruiserparts.com/42600a14-mercathode-kit

 

[DIY1111]

Hmmm. That does seem more robust than the wire-'thang. I'd have to drill a hole through my transom for the feeder wire. I could mount it right near where the current mercathode is. Expensive for the kit - I wonder if my mercathode 'sender' wired in the engine compartment is compatible with the hockey puck style one you referenced ?

 

[alldodge]

I installed them on my boat years ago and they do work. To not get into lengthy story, I needed more output, so changed from the Blue to the Black mercathode.

If you do decide to install, the one under the drive is disconnected, and the pucks are connected.

I bought the probe so can keep check. Then bought a lift so only use it to check others now
https://www.mercruiserparts.com/mercury-mercruiser-8m0135998-tester-electrode

 

[achris]

Chris. Thx. Totally know what it does although I do think that its an odd mechanism. Other than going to a mercruiser dealer to use an in-water, probe to see if it's actually doing its thing - you never really know. And, even that process is suspect due to all the the variables; loose marina electricity, other noble metals in the water etc... Wish you could could just touch the under transom mount exposed wire to a volt meter while on the hard and measure its effect..

Many years back I was a qualified subsea inspection engineer... So, that's some of my background. I am currently an (unemployed) ROV pilot... With air travel shutdown, I can't get to work...

So, I have a very solid knowledge of underwater corrosion, and it's causes and prevention. You could buy a silver-silver oxide half cell and test the system yourself. It's not hard to understand and check it.

The reason you can't check it out of water is because the system sets up a 'battery' with the salt water being the electrolyte. Out of water and the system is missing a component. That's why you can't test it while 'on the hard'.

What really surprises me it that only Merc have a system, none of the other manufacturers. I'd have thought they would have been all over it. Maybe Merc's patent has wrapped it up so tight the others can't make something that is sufficiently different that does the same job without infringing the patent... :noidea:

Chris.......

 

[DIY1111]

I agree it is a necessary evil. I have a decent understanding of corrosion ( self learned ), more regarding nobility of metals than 'loose' marina electricity. I try to minimize the exposure of more noble metals by properly painting them i.e. SS trim tabs, and props.

Without getting into those details and the focus of keeping a healthy mercathode system, do you think the transom mounted, 'hockey puck' is as good as or better than the under the transom mount system ?

Of note - my drive is extremely clean after 15 years of saltwater use ( 6-7 months in the brine a season - -1050 hours ). Most challenging drive-related thing, other than prepping the drive properly each season, is the mercathode 'wire'. Barnacles form under the wire, grow and push the wire out from where it's attached.

That's why the hockey puck is a thought. And, if I did this - would my engine mounted mercathode sender work with the hockey puck ? And, where would I mount this hockey puck to maximize its effect ?

 

[alldodge]

That's why the hockey puck is a thought. And, if I did this - would my engine mounted mercathode sender work with the hockey puck ? And, where would I mount this hockey puck to maximize its effect ?

The wire gets disconnected and the pucks gets mounted on each side of the drive (it comes with instructions). If you go that route, do the drill hole big, fill, let dry and drill smaller hole to protect transom

 

[DIY1111]

So - I can use my current Mercathode sender ? And, do you think just (1) puck would do it ? The surface area of my current mercathode wire looks tiny compared to the surface area of the puck.

As for potting the drilled hole - always - only way to fly. After restoring my boat and seeing all the core damage and delamination caused from leaking screws and holes.... I'm a preacher of potting with epoxy, then drilling through...

 

[alldodge]

Not knowing how the internal workings are of the pucks, I would use both, one on each side

Could also ask Merc to see what they advise