Adding additional Mercathode pucks?

[SeaNile]

My boat, 2004 Rinker 312 with Bravo 3 drives, does have corrosion on the drives and I want to do my best to preserve these drives because replacements are very expensive as we all know. So I have confirmed both drives have the Mercathode puck under the drive. Whether it's working or not I do not know at this point (boat is on land and shrink wrapped). I looked all around the marina today at other boats that also have the B3 drives, almost every boat had an additional Mercathode puck, some had two additional. The boats with twins had 4 pucks, two for each drive. Also spoke to a local mechanic at the marina and he also recommended adding the 4 pucks to my boat. Called Mercruiser and they recommended the additional puck per engine and said adding 4 total pucks would be a good idea.

So before go and have these additional pucks added, and I am leaning towards getting 4 pucks and replacing the existing Mercathodes and getting the red hi voltage controller....am I doing the right thing? I'll be changing all the zincs, Al, with the prop nut, sanding and painting the drives, etc.

Thanks for the help.

John

 

[Loneranger]

http://www.marinemechanic.com/merc/distributors/mercurymarine/sterndrive/corrosiontesting.PDF

http://www.reliabilitydirectstore.com/v/vspfiles/RDIStorePDF/RDI-Corrosion.pdf

http://www.reliabilitydirectstore.com/RDI-CRE-Corrosion-Reference-Electrode-p/rdi-cre.htm

Before you spend a bunch of time and some money on potentially needing more protection, I would test the protection that you currently have. The first link above is mercruiser specific instructions on how to test, the second is generic testing instructions from RDI. To test you will need three things - 1) the boat sitting in the water undisturbed for I believe 6 hours or so 2) a multimeter and 3) a silver chloride reference eletrode (which is the third link).

Having the silver chloride reference electrode is handy even if you need 4 mercathodes since you will need to test them in the future to make sure you are still protected (they wear out). Some people will respond to this and recommend the mercruiser specific silver chloride reference electrode which is fine but is not necessary and will be more expensive. A silver reference electrode is a silver reference electrode (heck if you really want I can point you to instructions to build your own).

John