Bravo III paint/corrosion

Black_Diamond

Up until 2 seasons ago, never had a spot of corrosion on my outdrives, blew an outdrive and had them both overhauled and added drive showers.  After that season corrosion all over the place..had it fixed/repainted, added a galvanic isolator, got a reference electrode and the Mercathode voltage was right in range, replaced both trim tab actuators (one was cracked..thought it was the corrosion source).  Pulled last fall..paint peeled off, lots of bubbles under the paint, but no obvious corrosion even under the bubbles.

So sanding and refinishing again, this time doing it myself with POR-15.  Could the drive showers be adding enough stainless to cause this?  other thoughts for peeling/blistering paint?

raybo3

Hey BD my first thought was the shower unless its another boat at your marina causing the problem. Maybe you should check the surounding boats with your probe. I have not heard any good stories about these showers.

TikiHut2

Can we assume it's in a saltwater dock slip? Maybe you're onto something with the SS drive shower reacting with the housing. 

Paint preparation is certainly a huge deal. Maybe the last paint job just wasn't what it should've been. 

It sounds like you've been through the whole thing but the other thing that comes to mind is the daisy chain of grounding straps that bond everything to the mercathode system. Sometimes a critical crimp on a strap can seem fine but might be compromised by corrosion(or missing) creating an isolated section (like the drive). 

I've seen a bit of new corrosion on our B3 so I'll be curious what you come up with.

Thanks, Mike

Black_Diamond

I'll be checking around my slip for stray current. I am in fresh water. I think tne drive showers just added too much SS. I thought they were a drive saver, but after each season they are a disaster to clean (plugged with zebra mussels) so at some point they are useless. I might pull them off before I go in the water. See what happens.

Tsquare

I tried POR 15 once,  It all peeled off within a few weeks.  I have since went back to Zinc oxide for the primer and Catalized Phantom black for drive paint.    Good luck but I will not go back to POR 15 again.  Let me know if it works for ya though.  Al

 

Black_Diamond

Al - What's your thoughts on drive showers?

Tsquare

As for the drive showers,  I started putting these on well over 5 years ago.  In fact I am the one who recommended these.  I really have not seen any additional corrosion due to the showers.  I suggest testing the water around the stern of the boat for electrolisis.  Do this periodically as more and more boats are launched and docked.  I suspect you have a gounding issue and stray current is forming.  Good luck  Al

raybo3

Al so how do you stop the showers from growth? I do not have them but reading a bunch of posts seems like growth and the holes plugging is a real problem....

Michael T

Hey JG, I have been using drive showers for 25 years on asphas, bravo Is, a blackhawk, and two sets of B3s. Absolutely no corrosion. and, in my opinion, there shouldn't be - even in salt water - unless there is something wrong with your paint OR you are in a marina that has a crappy electrical distribution system. The first time I ever had drive corrosion was two years ago when I kept my boat in a public marina.  A guy who owned a go-fast (expensive Fountain) forced the public marina to do a ground/stray current test. The electrician tagged the whole matina's elec system. Apparently he was white as a ghost as he said people could have been killed. I would do the following, lightly sand the damaged areas on your drives, wipe them with acetone to clean and prep them (acetone works chemically with Mercury paints), spray the drives with OEM Mercury primer( light coats) wait 24 hours, light sand between if you want, spray the drives with mercury OEM phantom black paint. Wait two days then wax and polish the drives. THEN make **** sure that no stray electrical currents are eating your drives. In my case the stray currents were also depositing a lime like substance (hard as rock) on my lab polished props. Because I boat in fresh water I also swapped my aluminum annodes for Magnesium annodes for much greater protection. Of course I'll probably have to replace the Mag. annodes each year.

BoatAway

POR 15 wont keep well in the water and won't stick well to aluminum drives. I agree with most people on here that say to check for loose currents both on your boat and in the marina. Boating Mag did a good writeup last month on how to do it fyi.

Black_Diamond

I did overcoat the POR-15, used the prep solution too. Guess we'll know in October. I just find it odd my anodes are just lightly pitted, almost no wear, yet pitted drives and on the SS props.

Michael T

BD unless I missed it you didn't say what your annodes were made of. You did say you boat in fresh water so you should have magnesium annodes. There is a big difference between the protection offered by "stock" aluminum annodes and magnesium annodes. All said, the cause of your problem still looks like stray elec. currents.

Black_Diamond

Yes all magnesium anodes. I'll play with my stray current device this weekend.

Michael T

Boomer, as usual, has put an amazing number of past posts on the THIS site from the "old" RBO site. There is a really good (but scary) article that he has posted as a link to that show just how bad the stray current issue is at most marinas and how the boats with fixed props (bronze.s.s. etc) will cause boats can stern drives (aluminum etc) to corrode faster. It looks like the best we can do is to isolate our own boats and hope the marina is agreeable to ensuring that its elec. system is a stray free as possible. Keep us posted!