Zinc question. Do our boats have a galvanic isolator?

[SeaNile]

With this nice weather I have a major case of boating fever.  Hoping to remove the shrink wrap during the last week of March and get in the water by April 7.  The boat is locked up and I am making my shopping list and am not sure which zincs are best for my Bravo 3 drives. 

It's a 2004 312 Rinker with AC and genset but I can't remember if the boat has a galvanic isolator.  I know this is important when trying to decide between Al and Mg zincs.  I'm on the C&D canal and pretty much stay in the Upper Bay area so at most I encounter is brackish water.  I know the salinity line changes depending on rain, wind, tides but I am pretty sure the Upper Bay (Bohemia and Sass) stays fresh water.

The mercathode system will be double checked this spring and if there is not a second system, I will be adding the second one for sure.  I want to make sure my B3 drives last a long time!

Thanks for the help.

John

[Dream 'Inn]

I definitely remember seeing the mecathode system on your boat.  As far as a galvanic isolator, I believe it should have it, and it would be mounted behind the circuit breaker panel in the cabin.  Definitely double check.

You should check around your marina to see what others are using, but I've heard Al is the new way to go.  I wouldn't use Mg if you were going into brackish water at all.   I may need to change my zincs out one of these days (still original I believe, but on a lift seems to help out as they hadn't even gotten to the crumbling stage), but I'll probably still be looking at using zinc.

[jmeyers278]

everything merc and volvo put out still say the same thing....mag for fresh water....al for brackish......zinc for salt..period...aluminum is not strong enough in fresh water

[l-skynyrd]

I was just thinking about andodes and saw this post. When I bought my boat and had some work
done on it my mechanic asked where I wes going to keep it.  Was told that at marina it was brackish water and put
alumium andodes on the boat. A year later had the boat pulled and had corision on props. The Al andodes were fine. My new mechanic suggested changeing to mag. It is hard to determine what is brackish and fresh. I am located about 60 miles up river from San Franciso bay (salt). I get about a 3-4 foot tide every day. I have swam in the water and never tasted salt. All I triing to say is you never know with out triing different andodes what will
work best. Talk to others in your marina, they will likely know from experiance what works best. I have not
pulled my boat in the last year and a half. I will be pulling it in the spring just to make sure
everything is ok for the summer. My boat stays in the water year round and I use it in winter every 2-3 weeks
just to keep the bottom clean. In spring-summer-fall almost every week, have not had growth problems.
When I pull it in a few months I will post what my andodes are like and maybe help someone here.
Eat your hearts out...I will be on the water next weekend.

Don't hate me......


Len

[alswagg]

Since the OP is located nearly 60 miles inland, I suggest starting with Magnesium anodes.  Test for 60 days, if you are seeing extream amounts of corrosion, at that time test with some aluminum anodes.  But I really believe the Magnesium will be you choice..   
On a side note, a couple seasons ago I had a new customer come in and talk about anodes.  He was doing business with a local dealership, as for anodes they installed aluminum only as the magnesium where too expensive and just corroded away year after year.  They told him if he was to install aluminum anodes, chances are he may never have to replace them again.  Consequently the Bravo gear case was severly corroded in need of a blasting, and reconditioning.
Now, anodes are inteded to be sacraficed, ie corroded away.  Rather than the gear case or SST hardware of the running gear.    With incompetant dealers and service techs at many marina's please check around before doing any large service.  Way too many people are getting gouged and incorrect diagnosis of problems.
Best of luck  Al

[FrankF]

There are tons of articles on the web regarding Galvanic Corrosion and Bravo IIIs that will teach you a lot.  I bought a new Rinker 312 in 2004.  Kept it in brackish water and ended up replacing my outdrives two years later.  Fortunately they were covered under warranty.  This is what you really need to know

     1. Aluminum Zincs for brackish water.

      2. Bravo IIIs are prone to Galvanic Corrosion because of the amount of dissimilar metals

      3.  The amount of stray electrical currents, which is the root cause of Galvanic Corrosion can vary greatly from   one Marina to the next in the same area

In my case the Merc Cathode system which is used to protect the drives did not generate enoough protective current.  To correct the problem additional anodes had to be added to my transom.  Since then everything have been working well.
Good Luck!!!