If there are not too many spots to repair I'd rather chip them open with a
screwdriver and let the water out (start with the nastiest looking one as a
test). Blisters can cause local fiberglass layers separation and form a good
entry point for water to start "working" your hull. If they are wet inside
chip the separated layer away, dry it with a towel and a hair dryer, apply
epoxy filler putty and gelcoat locally, sand it and polish out. Before
gelcoat you may apply a thin coat of ester-vinyl resin (cheaper then epoxy)
which is a superb if not the best water barrier. Your problem may be due to
manuf. gelcoat defect (3 years is nothing for a good gelcoat, unless there
are some accelerating factors like a poor original finish quality). I own 3
boats, 2 BR's and a cruiser (15 year old Bayliner, used in salt water as
well) with no single blister on any of them so far (in water for 4
mths/year). Painting the whole bottom with epoxy barrier will most likely
prevent the problem form spreading just like a thin coat of vinyl-ester (did
that 4 years ago on one of my previous boats, after application with a
roller it looked like an automotive cleat coat layer - good gloss,
spray-gun-like flow, minimal yellowing, do the test to see if you like the
results visually, water-barrier properties of vinyl -ester are just superb).
I prefer this over epoxy as you can put a gelcoat over vinyl-ester barrier
layer (this is what I ultimately ended up doing) as opposesd to epoxy which
has to be the top coat (gelcoat will not hold well).
Hope this helps.



"cc0080793" wrote in message
...
I have a 12' x 50' Catamaran Cruiser Houseboat, probably best described as
a
"camper" or "trailer" sitting on catamarans. Guess you might call it a
"poor mans houseboat" as it's not in the same league as the fancy $250k
jobs.... but suits our purpose beautifully, and we LOVE it.

I was told when we first put it in the water to watch for "blisters" in
the
fiberglass hull a few years down the road. Well... here I am a few years
down the road (3 years to be exact), and I DO see some half-dollar sized
places on the hull that must be the aforementioned blisters (3 or 4 down
each catamaran). Nice, smooth bulges about 1.5" in diameter that protrude
about 1/8" off the surface of the hull, almost looks as if there was a
carriage bold head under there that was glassed over.

Is this "blisters"?

What to do? Is this something I could fix myself, or does it need
"professional" work?

Some have said painting the glass hull with an anti-fouling paint will
help
prevent this, but I didn't think painting a glass hull was a common
practice.

Any and all suggestions are greatly appreciated.

Thanks in advance...

cricketman