Finally - I have a plan for dealing with Galvanic Corrosion on Bravo 3 - Comments

[xrochester]

This is my first season with the boat and my first time dealing with Bravo 3 corrosion problems.

Apparently, galvanic corrosion is ocurring unabated right now on my Bravo 3 on '97 250 Dancer. Many people commented on my photos saying it doesn't appear to be too serious at this point as long as I take measures immediately to stop it.
http://www.montanusphotography.com/bravo/

So after much research, here is my plan in order of importance. There are a million different opinions on all this, so I'm choosing the plan that seems to be the most informed. If anyone has any comments, please speak up.

1. Need sacrificial anodes. The ones on my boat right now don't appear to be correct because after 3 months in the water, they don't appear to be sacrificing. They very well could be the wrong metal. Replace with magnesium anodes.

2. Outdrive needs to be painted to cover bare metal. Green Zinc Chromate aluminum etching primer, Mercury Black enamel.

3. Galvanic isolation. Without this, it will render the sacrificial anodes useless when connected to shore power to prevent stray currents from exacerbating the problem. Thinking about this model: http://promariner.com/products/galvanic-isolation/prosafefs-series/

4. Mercathode. the blue model is currently installed on my boat, but I don't think it's working and/or installed correctly. Need someone to help me determine if it's functional. If not, I may install the more powerful red Mercathode.

5. Check the bonding system to see if it is functioning properly.

 

[techmitch]

If you plan on keeping the boat in the water I would highly recommend painting the drive assembly with anti fouling paint over the Merc . black. Also, as to your question about the functionality of your mercathode There is a tester. Let me see if I can find it.

 

[techmitch]

Here ya go. http://www.reliabilitydirectstore.com/RDI-CRE-Corrosion-Reference-Electrode-p/rdi-cre.htm and http://www.marinemechanic.com/site/page200.html

 

[Lazy Daze]

Are you sure there isn't already a galv isolator in your boat? Sea Ray would have put one in there.

Mg anode - fresh water? Just be sure that that is the best option. Often times, Al is better in many fresh water areas. Double check with locals who have boated in your water for AT LEAST a few years.

 

[Henry Boyd]

You should already have a galvanic isolator installed on the boat. It should be located very close to the shore power plug. I believe that some shore power plugs include the galvanic isolator function in the construction of the plug itself. In any event your AC wiring diagram should confirm this.

When you buy the new anodes I suggest you get a prop anode. This will require a new outer prop nut. You can buy this as a kit (prop nut and new anode) from boatzincs.com.

I also second the coating of the drive with a specialty bottom paint for aluminum. Most of us use Trilux 33. Buy it by the quart and glop it on.

Your mercathode may have been bottom painted by accident. When the boat is out of the water, put the drive up, crawl under the boat and look up at the bottom of the transom assembly. The wire on the mercathode should be bare and clean. If it is painted, get a chemical stripper and remove it. If the mercathode has been painted over it will still report everything is ok during testing.

Henry

 

[xrochester]

Are you sure there isn't already a galv isolator in your boat? Sea Ray would have put one in there.

Mg anode - fresh water? Just be sure that that is the best option. Often times, Al is better in many fresh water areas. Double check with locals who have boated in your water for AT LEAST a few years.

Yes, Freshwater. I just assumed there was not a galvanic isolator in the boat, but if there is already one there from the factory, that is great news. One less thing I have to deal with. Thanks for the tip.

 

[xrochester]

You should already have a galvanic isolator installed on the boat. It should be located very close to the shore power plug. I believe that some shore power plugs include the galvanic isolator function in the construction of the plug itself. In any event your AC wiring diagram should confirm this.

When you buy the new anodes I suggest you get a prop anode. This will require a new outer prop nut. You can buy this as a kit (prop nut and new anode) from boatzincs.com.

I also second the coating of the drive with a specialty bottom paint for aluminum. Most of us use Trilux 33. Buy it by the quart and glop it on.

Your mercathode may have been bottom painted by accident. When the boat is out of the water, put the drive up, crawl under the boat and look up at the bottom of the transom assembly. The wire on the mercathode should be bare and clean. If it is painted, get a chemical stripper and remove it. If the mercathode has been painted over it will still report everything is ok during testing.

Henry

Stupid question, but do you spray the trilux or brush it?

 

[sdarc]

Make sure all the bonding wires are there and attached

 

[Bugsy24]

Stupid question, but do you spray the trilux or brush it?

No Question is Stupid.... use the Brush on, the spray does not last very long. You'll usually get a full season out of it!!

 

[Henry Boyd]

Marshall beat me to it. Brushing it on last longer and is actually cheaper as you can get several seasons out of a quart, and basically one application from a spray bomb that just barely coats the drive.

Henry

 

[xrochester]

Not sure if this is a success story or not yet, but after three weeks back in the water, no signs of any new galvanic corrosion on the outdrive after installing new magnesium anodes (turns out the old ones were zinc), a propshaft anode from boatzincs.com and the red mercathode system. This was without shorepower being hooked up. I did not paint the outdrive yet, so much of it is still bare aluminum. As some suggested, the boat must have a galvanic isolator installed from the factory. I looked up the schematics on similar models/years and they all indicate this in installed. No reason mine wouldn't. So that's one less thing to worry about. Just out of curiosity though, we'll see what happens with shore power connected now, if it makes any difference. One little footnote, the more powerful red mercathode system ran by batteries down, hence the reason to re-connect to shore power! duh!

 

[techmitch]

Not sure if this is a success story or not yet, but after three weeks back in the water, no signs of any new galvanic corrosion on the outdrive after installing new magnesium anodes (turns out the old ones were zinc), a propshaft anode from boatzincs.com and the red mercathode system. This was without shorepower being hooked up. I did not paint the outdrive yet, so much of it is still bare aluminum. As some suggested, the boat must have a galvanic isolator installed from the factory. I looked up the schematics on similar models/years and they all indicate this in installed. No reason mine wouldn't. So that's one less thing to worry about. Just out of curiosity though, we'll see what happens with shore power connected now, if it makes any difference. One little footnote, the more powerful red mercathode system ran by batteries down, hence the reason to re-connect to shore power! duh!

Bare aluminum, in the water, on a BIII drive... Doesn't sound like a very good plan to me!

 

[zeehond_nl]

Do you have a picture of the place of the pucks from the red controller? I also thinking about black,blue or red controller. Are the pucks made of good (strong) material? Because replacing them every few years is not mine thing.

gr MArco

 

[xrochester]

Bare aluminum, in the water, on a BIII drive... Doesn't sound like a very good plan to me!

I didn't want to do an extensive paint job on the lower unit 3 weeks before the boat is due to come out of the water, I plan on pulling the drive and doing that over the winter in my workshop.

 

[xrochester]

Do you have a picture of the place of the pucks from the red controller? I also thinking about black,blue or red controller. Are the pucks made of good (strong) material? Because replacing them every few years is not mine thing.

gr MArco

No, but I will when the boat comes out of the water.