Bravo III and corrosion

[torcano]

I've become aware that Bravo III outdrives have had problems with corrosion in the past. Has this problem been resolved with the later year models (2004) that have the mercathode system? Other than changing the zincs every year, is there any other preventive maintenance to be done?

 

[TilliamWe]

Re: Bravo III and corrosion

They have Mercathode for a lot longer then 2004 and later. So don't believe that it is some miracle cure. (My 1997 has Mercathode, and I'm not sure when Mercathode started, but it might be as old as when the Bravo series was introduced in 1989ish)
Mercruiser developed and released Sea Core for the 2008 model year that is supposed to solve all their corrosion problems. So while they made running changes to the drives, (2nd ventilation plate anode, propnut anode, and changed the rear bearing carrier and it looks green) what do you think that means for all the B3s produced prior to Sea Core?
Plain and simple, you have to pull the props off any used B3 to check for excessive corrosion on the rear bearing carrier.
You don't want it to look like this:

But again, Please Note, that drive is fully functional, no problems whatsoever. So they can look ugly, but not be bad.

That corrosion happened in two summers (April to October), in freshwater, at a 30 year old steel framed slip, when I was turning the batteries (and thus the Mercathode) off.
Now my annual maintanence includes:
Repaint the drive,
Clean off the "Freshwater only" anodes ( I will end up replacing them every other year)
Leave the battery on

Corrosion has not progressed in 4 years.

 

[torcano]

Re: Bravo III and corrosion

Thank you. I just bought my boat and the outdrive was inspected by a certified marine surveryor. There were no signs of corrosion on the outdrive. The 2004 boat is kept in salt water for 6 months and then dry docked. I am a new boat owner but have been around boats for many years. Now it's my turn to worry about proper maintenance. I understand the zincs should be checked every month. I plan to change them every season. Anything else I should be doing to avoid expensive problems down the road?
Bob

 

[Don S]

Re: Bravo III and corrosion

Get the proper Mercruiser aluminum anodes, not the aftermarket "Zinc" anodes. Also make sure your Mercathod system is hooked directly to a battery so it will work while the rest of the systems on your boat are off.
Here is a link to the corrosion protection section of a service manual. Your's is newer, the the info on testing the Mercathode system is the same.
Corrosion Protection

 

[torcano]

Re: Bravo III and corrosion

Don,
Thanks alot. That link was very helpful. I have the second part of my marine survey (sea trial and full engine check) next week. I'll be sure to have the surveyor do a continuity check of the mercathode system. My marina is doing the outdrive service, including "zinc" change. I'll see if I can get them to use aluminum anodes. Whatever they used for the past 4 years seems to have worked.
Bob

 

[bigbrownbuku]

Re: Bravo III and corrosion

paint the housing in tilliams pictures first with zinc chromate then with phantom black. it will keep it corrosion free far longer then the right anodes and a mercathode. also paint the upper gearbox where the top cap joins and where the rear cap joins.

 

[HT32BSX115]

Re: Bravo III and corrosion

There is a Mercury service bulletin that outlines the "new" anode material. It's not so new. That SB came out in something like 97 or 98 and changed everything to Aluminum. The cheap (after market) anodes are sometimes not aluminum. This is one case where one should probably use the Mercury OEM anodes.

Also, it is imperitive (as outlined in the Mercathode instructions from Mercury) that you have the system checked in the actual slip where you're going to park the boat and that you check it in a month or so after set up to ensure that it's still working correctly.

If the Mercathode is set up wrong, it can actually accelerate galvanic corrosion!


If I was going to "slip' my boat in salt, I would get the tools to check it myself and I would check it every time I went to the boat. Even your "next slip neighbor" can do things that will change things for you in your slip. If you're in salt water that is moving like the marina near Tacoma Narrows or other places where tide moves the water rapidly, The Mercathode may not protect as well as in still water or may not work at all.

I love the Bravo III. I park mine in my hanger.


Regards,




Rick

 

[torcano]

Re: Bravo III and corrosion

I will be keeping my newly purchased boat in a diiferent marina about 20 miles away. Rick, the testing you referred to I assume means using the Mercathode reference electrode and a digital voltmeter as descrbed in the service manual link Don so kindley provided. Do you suggest a particular brand and model for the meter? I understand the Quicksilver VOA meter is no longer available. Is the Mercathode reference electrode a standard item that can be bought in a marine store. Thanks

 

[HT32BSX115]

Re: Bravo III and corrosion

I would think just about any good VOM would work. The service manual talks about measuring in mV (Millivolts) That's Thousandths of a Volt! The range they recommend using it the 0-2 Volt range (0-2000 Millivolt) The voltages you're measuring are on the order of 8-10 MV or so. not much!! You need a multi meter that is fairly accurate down that low.

EENGR types like me are partial to Fluke, Techtronix, Motorola, Beckman, Singer, ETC ETC $$$, the GOOD (expensive) stuff!! . I have a Fluke 189 but you probably don't need one with all those bells and whistles....

Service manual 11 in the corrosion section says to NOT use an analog meter.

While there have been analog meters (VTVMs) of yesteryear that are VERY accurate (when calibrated) you're not likely to find one.

Mercury suggests a Radio Shack multi-meter...... uh......I wouldn't be caught dead with one of those in my pocket! but that's me!! They're probably ok.

http://www.boatfix.com/merc/Servmanl/11/11a7r5x.pdf

 

[torcano]

Re: Bravo III and corrosion

Thanks again. I'll do some research and try to locate some accurate and reasonably priced meters. I assume the Mercathode reference electrode is standard.
Bob

 

[Bt Doctur]

Re: Bravo III and corrosion

also if painting the bottom, keep at least 1 inch away from the transom housing, there is an additional bonding kit available too

 

[Mischief Managed]

Re: Bravo III and corrosion

I bought a Mercruiser magnesium anode kit for mine. It's the popular option in the fresh water I boat in.