Brian,
You need to be working with a good Merc. shop. Your engine installation
needs to be checked for proper grounding. The Mercathode needs to be
checked. If the Mercathode doesn't seem to be working, move the boat away
from your marina and retest. All zincs are not created equal. If you are in
fresh water you need magnesium or aluminum. Your AC system needs to be
checked. Do you have an isolation transformer? Is there stray current from
another nearby boat?
JIMinFL
"Brian Saucier" wrote in message
...
Hello All,

It has been awhile since I posted or subscribed to this newsgroup. I
hope everyone is well and enjoying their boating season.

My season just took a setback ... as my boat (2000 SeaRay Sundancer
290)
is sitting on blocks, awaiting delivery of 2 new lower units for my Bravo
II
drives. Severe corrosion, despite changing all sacrificial anodes, every
9
months, caused major cracks along the 'bullet' casing. There are two
cracks
on each side of the twin I/Os that are severe. Generally the drives'
lower
ends (only 4 years old have pretty much disintegrated. So .... estimated
~$8000 later, I'm wondering what the heck happened ?!!?

Some facts: I have a reverse polarity indicator that never shows a
problem from my shore power.
However, the marina was flooded last year after a hurricane and the
'light
and GFI doesn't work' on the shore power box ... and I suspect stray
current - but don't know how to check it (mostly fresh bayou water).

My neighbor boats (only 2 others nearby) seem to not even use their
shore power much.

How does one 'check' a Mercathode system on my boat to make sure it is
working correctly ? I really want to rule-out anything going on in my
boat
and the slip before I return with new drives.

Thanks in advance to all that provide me advice !!!

Greatest Regards,
Brian