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Originally Posted by Dave R
I have one of the "Bad" Bravo 3 drives. The biggest mistakes with these drives that lead to corrosion (in Winnipesaukee anyway) are not knowing to leave the battery switch on and not changing to proper freshwater sacrifical anodes. {snip} If you have shore power (not likely on a 220 Sundeck), it's a very good idea to install a galvanic isolator to stop low the voltage DC from riding on the AC line. That DC can overcome both the mecathode and the anodes and do some serious damage. |
Switching to magnesium "zincs" is a must for Winni. There's no reason not to have them on any boat. The Mercathode system is something of a mixed bag IMO. According to Mercury it should be connected directly to the battery but if it isn't and you have to switch the battery on, then you have more potential problems. Combine the Mercathode with a CO detector and perhaps other stuff that's now drawing current and they'll drain a typical starting battery flat in a week. Brand new batteries and deep cycle models (only applicable if you have a 2 battery system) tend to last longer I'm told. If you have a 2 battery system you'll want to be careful to switch on the "correct" battery. The auto bilge pump is often only connected directly to 1 battery. If this goes dead then your bilge pump won't run if needed. Run your Mercathode + stuff off the other battery (if you even have one). So now your battery might go flat, and even if you aren't worried about the bilge pump, you'll want to avoid leaving your battery that dead for any length of time. Next you'll want a charging system for the battery that's left on. If done improperly this can be the worst thing for your BIII. DaveR is spot on re: needing a galvanic isolator if you're going to leave your batt(s) charging up on shore power. Perhaps a really low power solar cell might be an option. And again ditto on the outdrive paint ! I've got to get ours done this year.
FWIW - I recall Mercruiser doing some changes to the BIII in 2000 or 2001 but I still see many complaints re: corrosion on these newer units. While I'd guess that stray currents in a marina environment, salt water and poor maintainance account for a good number of these, it makes one wonder. Especially since Mercruiser specifically states there is no corrosion problem on the BIII and it's all the customer's fault if anything goes bad. They want a galvanic test performed weekly and daily checks on the "zincs". That's just plain silly, even in salt water. Luckily here on Winni, what I think is a poor design, is not as "stressed" as it would be elsewhere.