My carrier looked worse than this and Mercruiser replaced both lower units under warranty (I just made it before 2 years were up). I agree that there should be some way for the system to automatically monitor Mercathode function however stray current in the water can also erode the drive even when the Mercathode is working correctly.

 

I agree 100%. I bought a tester last month and learned how to use it. I can't see any other choice.

 

This is my second lower unit. The first was replaced by Mercury under warranty a couple of years ago because of similar corrosion particularly on the bearing carrier. All I know is this appears to be a losing battle with no good resolution on how to stop this problem in the future. I meticulously maintain my boat and my outdrive. I pull the boat out of the water every six months and paint the outdrive if there is any corrosion on it. The last time it was out of the water the drive had only minor corrosion with virtually none on the bearing carrier (which is why it is unpainted in the picture above). So far Mercury is not inclined to replace the lower unit again.

 

Lets face it, the BravoIII has/is a major design flaw, I don't care what spin anyone puts on it. Too many dissimilar metals creating galvanic corrosion at an alarming rate. They are designed for freshwater, put them in saltwater, tie the boat to a slip then watch them turn into powder. The Mercathode, in my opinion was an afterthought, I can imagine the Mercury engineering department frantically scrambling around to come up with a way to correct this flaw and here we go the birth of the Mercathode. I see plenty of boats with Alpha drives tied at the slip in saltwater for years with only the standard anodes protecting them, no problems. These Bravo III drives are making a fortune for those that profit from repairing and selling them, this is what they are best at.
I had to pay Mercury over $100 for a crappy test probe that looks like a cheap children's toy that is used only for measuring the MV in the water produced by the Mercathode. I bought the test probe not only to verify that the Mercathode control unit is still producing voltage but I also need to verify correct output when the barnacles begin to attach themselves to the outdrive and Mercathode. Who knows if it still works all covered with crude, then who knows if it will be damaged if I need to clean it mid season.

 

I wonder if the SeaCore drives are free from corrosion issues?

 

Can you paint bearing carrier?Couldnt hurt could it?Mine looks about the same shape fresh water only.Its on wet slipped about4-5 months and anodes and paint is every year thing.

 

Yes................I primed and painted it. It is made out of aluminum but has some type of coating on it that is supposed to inhibit corrosion.

Dave

 

I brought my out-drive home at the end of last season and over the winter worked on it. I sanded it and within minutes (too avoid oxidation) painted it with Interlux Primco (3 coats 1 week between each coat) then painted it with Interlux Pacifica Plus (again 3 coats 1 week apart). At the end of this season if there are signs of new corrosion on my OD I can honestly say that I did everything I could to prevent and will probably look for another boat with a non Mercury OD. I'm really hoping this works because I have the rest of the boat exactly the way I want it.

 

DICOR................I really don't think that any paint we can apply as DIYourselfers will stop the corrosion. It will only slow it down. The factory paint is better than anything we can do at home but it still bubbles and corrodes from the electrolysis effect of aluminum and stainless. I change my anodes every year as well and they take the brunt of the corrosion IF the Mercathode is working properly.

Mercury could probably nip the corrosion in the bud if it put aluminum props on the B3. But my understanding is aluminum is not strong enough to stand up to some of the forces generated on the props by larger boats. I have also seen a number of threads where some people have coated their SS props in the hopes of slowing down the electrolysis.

All I know is when something fails on the Mercathode, you shouldn't have to find out six months later by looking at a bunch of corrosion on that expensive lump of metal that propels your boat. That's why I am advocating that Mercury try to develop some type of failure warning. It may not solve all the corrosion issues caused by stray currents and the like but it would be a step in the right direction.

And it also puzzles me why Mercury hasn't made Sea Core their only offering if it is superior in corrosion resistance.

Any Sea Core owners out there who can tell us what they have experienced?

 

Any Sea Core owners out there who can tell us what they have experienced?

Dave, Obviously I am not an owner but not sure if you remember that 32 or 34 foot blue hull boat they had at the marina for repairs about 1.5-2 years ago. It was not a Sea Ray, maybe a Rinker or Four Winns? It had twin Sea Core Drives. Anyway, I was talking to the boat owner and it was only a couple years old and Mercury replaced both of the entire outdrives (including Transom assemblies) under warranty due to corrosion. As I recall, it came from Lake Norman and was headed to Lake Murray after the repairs. I think the drives were only a year or two old at the time and corrosion was in the early stages but still noticable. Probably the first year they had Sea Core drives. As part of the replacement they installed the Heavy Duty Mercathode along with the transom pucks on both drives. It had none previously.

So to answer the question, yes they corrode too.

 

I installed the High Output Mercathodes on my boat last summer. With the standard Mercathode I tested right at the low end of the acceptable range. There is a lot of stray current in my marina. I noticed a big improvement in the amount of corrosion when I hauled the boat this spring. The mechanic that installed the new Mercathodes mentioned that he previously worked for Hall Marine at Lake Wylie. He said the marina there had huge amounts of stray current and that many owners upgraded the Mercathodes due to corrosion issues.

 

I would agree it would be nice if Merc could put some type of sensor in the water to measure the electrical current. The issue is the sensor will draw even more current to the boat. It is physical fact the electrical current follows "the path of least resistance."

If you like to know how to perform the test here is link: http://www.mercstuff.com/mercathodetest.htm. This same site has additional information for those of us lucky to have the Brovo IIIs http://www.mercstuff.com/bravo3corrosion.htm

Also, found a thread where a fellow boater and DYIer repainted his Brovo III. I think he really needed to take the outdirve off and paint the drive and gimbal assembly separately. He is going to miss areas that have he should paint. Also, he states that Merc instructed him to used some automotive products. I am not sure I agree because I don't know how well those will hold up in a water environment. I have heard of guys doing this same process but using tractor paints having success. Tractor preps, coating and paints can take several days to cure and are design to be exposed more so than automotive paints. I can understand why someone may consider using it on an outdrive. Here is the link to his project: http://www.boatingabc.com/forums/ubbthreads.php/topics/484140/1.html I should also note in the end he did not go with automotive paint but got his paint from supermarince.com

 

Jim, do you happen to have your parts list? Also, I am just down river from you at Mt. Island.....

 

Here is link to the kit

http://www.mercurypartsexpress.com/us/mercathode-kit-p112015.html

 

Jim T - I also have the high output controller along with the transom anodes and my boat is slipped at Lake Wylie Marina. And this lake is really bad when it comes to corrosion.

Dave

 

Fact of the matter is no stern drive boat should be stored in the water for long peroids of time. Stern drive boats should be on a trailer, on a lift, or in high and dry. IMHO if you want to keep the boat in the water buy an inboard.

 

Get to work you slacker!

 

I agree with the 'is it working' portion of this post. My boat doesn't have Smartcraft so that wouldn't help me BUT, could there at LEAST be an LED somewhere so we could verify the circuit is complete? Since its a DC component, I've been thinking of wiring an LED into the actual electrode circut to so that if is ON, I'll at least know that the unit is functioning. It really looks like a rinky dink device, a paper clip sized piece of wire to do the job. A little marine growth and its inerted.

 

Do all B3's have this? Anyone have a picture of it mounted on the outside of their boat?

 

Perry you caught me surfing at work. Got to go. Wait a minute shouldn't you be waxing the boat and not surfing too?

 

The problem with detecting a "working" mercathode, from my understanding, is that you have to test it from outside the system (i.e. outside the boat). It's not just a matter of "is there power to this", but "is it creating the requisite 'field' in the water". What you are talking about doing is basically permanently wiring up a mercathode tester, which involves sensors held away from the affected areas of the boat.

The joyous part of this is that these are electrical/metallic objects, which mean that THEY are now part of the system that is doomed to fail at some point. And they might be able to fail "good" (i.e. they show that they are still working).

The only reliable test I can see is a regular inspection.

 

Permanently mounting the tester on the outside of the hull would bring the test probe to an early demise, they are not made to be pulled thru salt water at 40mph. Now if you are determined to install a test probe maybe you could attach it to the ladder on the swim platform and when you want to check the Mercathode flip the ladder out and take your reading. But honestly the easiest way to check it is to lower the probe into the water connect it to a Fluke meter and take your measurement. Once your done be sure to rinse the salt water under fresh water to keep it from corroding. It takes less than 5 minutes, time well spent.

 

All was surfing youTube and came across this video. Thought it was interesting and that you guys might like it as well. Now, I don't know that those of us with B3s will ever "fix" the issue as he describes in the video but at least he shows how to test and some things you can try to reduce the rate of corrosion. Here is the link: http://www.youtube.com/watch?v=NqzWdOAeHG8&feature=channel&list=UL

 

Since first posting about this, I decided to get my own test electrode. I was able to confirm that my system is currently not providing the protection it should. I had a reading of approximately 630 mv which is below the recommended rate. Since I still have the extended Mercruiser warranty, my dealer will begin looking at the problem. Once it is located and remedied I will be testing at least monthly.

I still don't like the fact that an owner has to be so proactive just to make sure his drive is adequately protected. There has to be something Mercury could do to at least alert the owner he may have potential problems without having to do an external test on a regular basis. Either that or get rid of the problem by developing aluminum or composite props for the Bravo III thereby eliminating dissimilar metals altogether.

Dave

 

Aluminum and carbon fiber together? That would make stainless steel look like a holiday. You might be able to design a prop out of Titanium, but it would most likely be cost prohibitive.

Look at the pod drives, last I remember most were made substantially from Nibral (Nickel-Bronze-Aluminum) as well their props. Should perform well... Imagine a Bravo3 with all of it's outside parts made of Nibral?

 

It is stunning to me that folks have had these issues for so long, yet no REAL resolve. I've got a pair of '98 Bravo III's on my boat that I have to do both carriers and a reseal.... And I see boats with the same issues after 1-2 seasons. I wonder how many times mine were fixed/replaced!

 

It is stunning to me that folks have had these issues for so long, yet no REAL resolve. I've got a pair of '98 Bravo III's on my boat that I have to do both carriers and a reseal.... And I see boats with the same issues after 1-2 seasons. I wonder how many times mine were fixed/replaced![/

When i kept the boat in NE i kept it in the water all year, like the op, i had it short hauled twice a year to do zincs and a fresh coat of trilux - at that time i also cleaned/inspected the mercathodes - i put 10-15 hours of my labor and $500 - $1000 (not counting the cost to haul) into maintaining my drives each year - to this day my drives have 0 corrosion. Now my boat is stored on the hard and is only in the water when i use it (1 week to 1 month at a time) this has drastically reduced the time and cost of owning/maintaining a twin sterndrive boat. You can say the resolution is either fanatical upkeep, an inboard powered boat (which still requires upkeep), or no boat at all. All boat systems (and the hull) need constant upkeep or they will fail, some just sooner than others.....sorry for the ramble, dont really know if i added anything meaningfull here - its 3:16 am and im up with a cold....

 

I can't believe it. Last year I had my Mercathode assembly replaced because it was not working. I had the transom assembly replaced this past winter due to corrosion. I checked the Mercathode 2 weeks ago it was working fine. Checked it yesterday and nothing!!!! I'm starting to realize these things are crap and I'm suspecting the majority of them out there may be bad!!!! I now know why Mercury sells the Mercathode test probe at such a high cost, they don't want their B3 owners out there checking them for fear of a mass revolt.

 

I have SeaCore B3's and am in a very corrosive environment - so far not a HINT of corrosion - despite 1 mercathode was not working for 6 months (until I got my tester)

But I do chew through anodes - I change every 6 months.

So far boat has been in water 1 year and 2 months - and holding up fine.