On Sun, 3 May 2009 21:34:14 -0700 (PDT), joost
wrote:
could be more unknown electrical leaks - esp if blisters are round.
Could also be 'salts' - we don't have products for it, but do have an
info page with links on it explaining it.www.epoxyproducts.com/salt.html
paul oman
progressive epoxy polymers
Hmmm.... yes, the blisters are definitely round. And it happens only
at and below the waterline. Probably you are right and there are more
electrical leaks. Actually, I also found that there is a potential on
the hull, so something else must be leaking. It is a very frustrating
problem. It takes so much time to repair all those blisters and if I'm
unlucky I've to replace the propellor again too 
Thanks anyway,
Joost.
An acquaintance had the same problem and painted, or partially painted
the boat several times - about once a year if memory serves. I asked
him several times whether he was sure that the hull was totally
isolated from the electrical system and he kept assuring me that it
was. His mate checked it!
After he had spent God knows how much money on yard costs he
apparently found another friend who repaired what ever problem was
leaking electricity and from what I hear (he's sailed for S. Africa)
is having no more paint problems.
I'm not a steel boat guy but I'd make very sure that the entire
electrical system IS isolated, radio grounds not forgotten and
remember that the engine has to be electrically isolated, before I
started looking elsewhere.
Cheers,
Bruce in Bangkok
(bruceinbangkokatgmaildotcom)