Daniel,
There have been a lot of discussions about using SS below the water line as
well as using SS with other metals in an electrolyte solution (salt water).
The arguments boil down to the susceptibility of SS corrosion. In the
absence of electrolysis, SS protects itself by using excess oxygen in its
environment to create a thin skin of corrosion, which prevents additional
corrosion. If abrasion through mechanical movement abrades the skin and
additional oxygen is available, it self heals. If the surrounding
environment is oxygen depleted because of the lack of air or water flow
around it and mechanical abrasion occurs, corrosion is very rapid and
severe. This is commonly called crevice corrosion. In addition to this is
electrolytic corrosion, the first mentioned case. This is where the
dissimilar metals in an electrolyte create an electric current which erodes
the most anodic metal at a rate according to their difference in the
periodic element table.

Now, in your case, you know nothing because you did not build it yourself.
You observe a staining which could be corrosion. You have been told your
keel is lead and the bolts are 316. You have the prime ingredients of both
corrosion cases. You have no peace of mind here without keel removal. Can
you afford the loss of the boat or possibly even the loss of life? Your
call.
Steve

"Daniel" wrote in message
...
I recently hauled my boat and after few days I noticed allarming coloured
streaks oozing out of the thin crack (very thin and of little concern by
itself) between the keel and the hull.
The colour of the streaks is green-blueish, something that suggests copper
sulfate, and sort of shiny that suggests micro-cristals.

According to the boat makers the keel bolts are AISI 316 SS and the keel
is of lead.
The boat was made in 1978.

Do you have any suggestion? Do I have to drop the keel and check the
bolts? I would rather avoid it, if not really necessary.

Thank you
Daniel