Galvanic corrosion on Brovo 111 outdrive 2004 342

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 The  drives were new in 2004 and  and used mostly  in fresh water and connected occasionally to shorepower ( once a week for charging batteries and friges prior to weekend trips ). For the past couple of years I have been touching up the drives after seeing some corrision on sharpe edges. I have replaced the anodes  a few times with very little corrosion shown on the anodes. I check yearly for good grounding of the anodes and touch up the paint a couple of times a season.
  My shore power is GFI protected with  all the proper grounding   and never have any other boats on my dock plugged in .  I travel  in  salt and brackish water a couple of times a year but never connected to shore power then  .
 I see other drives of the same age with no corrosion  in our fresh water .
 Questions
 1/ Will it do any good  for the drives to add anodes to the   trim tabs?
2/    These units  don't have the prop anode ,should I add that ?
3 Where is the fuse for the MerCathode protection ?
4  Would my boat have an galvanic Isolator?
If not should I consider one for the few times I connect ?

[alswagg]

Use Magnesium anodes in Fresh water,
Aluminum anodes in brackesh
Zinc in Salt. 

Fuse for Mercathode should be connected to constant power at selector swithc
The Boats electrical system has a built in galvonic isolation system.
Adding the prop shaft anodes can only help.
If you wish to add anodes to the tabs, they need to be grounded to work properly.
Al

[mightys4]

What Al said....

I just finished my annual Bravo III recondition, mine is a 2002 and its in frankly bad shape at this point, I think its the last year, my lower is in terrible shape.  As opposed to you, all the boats on my dock are plugged in, and I run more than anyone, some of the boats last year I never saw go out, I really didn't get it, why spend all the money?

I have magnesium as I'm in fresh water, it had aluminum on it when I purchased it, which was wrong, they were barely touched.  This year, the mag anodes were beaten up, so they did the job.  Definitely get the prop anode, as the props are attracting a lot of the problem, its a lot of stainless on an aluminum housed drive, the stainless shaft also attracts...

I'm with you, it kills me when I walk past all these other boats with minimal or no work to do, and it takes me 8 hours to get the drive cleaned up for the season...  Good luck.  I've had very good luck with www.boatzincs.com, the prices are excellent, the ship same day and its brand name product, everything lines up and they have the prop nut zinc you need.  No affiliation other than a satisfied customer who really liked the prices and service, your mileage may vary, one time offer....

cheers!

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 Thanks for the replies
  After a lot of reading, one the issues I have JUST found out that  the MerCathode  shuts off with the   Battery switch. I  have always shut this off when the boat was not in use.  I found this  info in The marine Corrosion Guide put out by Quicksilver.
  I will add the prop anode and now leave the selector switch on  as well as check the fuse

 Thanks again
 

[bat32]

Thanks for the replies
  After a lot of reading, one the issues I have JUST found out that  the MerCathode  shuts off with the   Battery switch. I  have always shut this off when the boat was not in use.  I found this  info in The marine Corrosion Guide put out by Quicksilver.
  I will add the prop anode and now leave the selector switch on  as well as check the fuse

 Thanks again
 

I didn't think it would shut off with the batteries?  I thought it was wired to a constant hot.

[alswagg]

The Mercathode is supposed to be hooked to the B+ constant on side of the selector switch.   You can check this by measuring the voltage at the Mercathode module.  B+ should have voltage while battery switch is either on or off.  Al

[ruwallydog]

This thread is worrying me. This is my first off season with the boat and even though the previous owner touched up the drives before the start of last season they were in bad shape when I pulled the boat in October.

Just spent the better part of two days sanding, priming, and painting the drives. Maybe I better have the tech hold off on splashing until he can check out the Mercathode.

[politby]

Princess V42 next to me in the storage facility with both lower housings completely gone (Volvo DPS). Gears and innards on the bottom of the sea presumably. Last boat to be hauled last fall - came in completely covered in snow and ice.

Shore power problem, according to the mechanic. Owner neglect, my take.