Mercathode Controller Blue vs Black

[clawless1]

I cant seem to find a clear answer on this....

I understand the black controller is the least powerful and is intended for the system with the two pucks on the transom, the blue controller is more powerful and intended for the gimbal mounted anode.

So the question is, can you use the blue controller in place of the black controller? If not, why not?

 

[alldodge]

Re: Mercathode Controller Blue vs Black

I cant seem to find a clear answer on this....

I understand the black controller is the least powerful and is intended for the system with the two pucks on the transom, the blue controller is more powerful and intended for the gimbal mounted anode.

So the question is, can you use the blue controller in place of the black controller? If not, why not?

Your correct about the controllers, and you can use either with either setup. A boat with minimal electric load and aluminum prop can be ok for the black. Boats with stainless props and more load get the blue. I installed an additional blue one with exterior through hull anodes due to bravo 3 and lots of load, galvanic corrision was an issue. They just draw more juice when working but not much more.

 

[clawless1]

Re: Mercathode Controller Blue vs Black

Thanks! I'm hoping the blue ones will last longer as well being more powerful. We have a lot of issues at the marina and several people have these fail with regularity and after a week, bravo3 prop nut anodes are bubbled up to twice their size on several boats. While it brushes off, I don't think its normal. We (the slip holders) think its bad wiring on the dock, the marina 'said' they had it checked and there were no issues however they promptly put up 'No Swimming' signs. Several of us have talked about moving however they have a prime location - what can you do.

 

[alldodge]

Re: Mercathode Controller Blue vs Black

Sounds like you have a real large problem in the grounding department.
Most the time the boat being damaged by galvanic corrosion is caused by other boats and electrical connections (marina) around them. If your boat is maintained and well grounded, stray electrical currents from other boats, shore power connections will be drawn to yours. Hooking up more items which draw power only makes you more susceptible. If you were not connected to shore power there would be no galvanic corrosion because you would not be grounded. There are two ways to stop or diminish these stray currents. Your boat needs to produce sufficient apposing current to make your boat less appealing, so to speak. Galvanic isolators should be installed to isolate your boat from external ground. A GI is a device that is inserted, in series, into the green grounding wire (safety ground) of your shore power feed to help minimize stray direct current / DC from flowing into your vessel. While blocking stray DC current it also has to allow for the passage of AC fault current. Dissimilar metals cause corrosion as well, aluminum casings and stainless steel props. A stainless steel prop makes a boat more attractive to stray currents then aluminum prop. Your boat needs a Mercathode installed at the least if one is not already there. Installing a galvanic isolator would be next.

My boat is in fresh water at a well kept marina, has a bravo 3 drive and stainless steel props. Every year when I pulled the boat for storage and pulled the props my hub was being corroded. Every year I would clean and prep the hub, re-prime and paint the hub, and the next year find more corrosion. After research I obtained the Merc test probe and found I was not producing sufficient apposing current to stop the corrosion. The next year I installed an additional Mercathode and two anodes in the hull mounted on each side of the drive. With the additional Mercathode I was able to get the field up to where the corrosion stopped.

Field currents and tech spec is listed below.

http://www.boatfix.com/merc/Techbk/97/97hs7.pdf

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

To find out who is leaking power into the marina you need a Leakage Current Clamp Meter. Put it around the power codes going to each boat and see what you read. If the meter reads zero then no leakage, any thing above zero is being leaked into the marina.