If you use silicone (above the waterline please) don't initially tighten down
the fasteners all the way. Leave a thickness equal to thin cardboard, let it
cure completely, and then tighten the fasteners. This forms a gasket to seal
the fitting. Putting on silicone and then tightening everything up just
squeezes it all out and then leaks start in short order.

Polysulfides are known to attack many plastics, so for plastic port lights etc
you are really left with silicone. I would not use 5200 with anything you might
ever want to take apart and not wreck the fiberglass. I've seen the stuff pull
off gelcoat.

JJ

" wrote:

Wow! I didn't know you shouldn't use polysulfides with plastics. Given
that little tidbit, I think I'd try their 4000UV product (after finding out
what it is.) I've had trouble with silicon leaking, including marine
varieties, and don't buy it for anything anymore...just walk right past it
and buy something else.

Brian


"Jerry W" wrote in message
...
I've had very good results with silicone rubber sealant. I note that West
Marine's catalog guide section specifically recommends against using
polysulfides on plastic and this confirms my experience. The sealant never
really cures at the interface with the plastic. Their catalog features a
3M
product designated 4000UV which is "highly recommended for ABS, Lexan and
other plastics". I have no experience with this material and would be
interested in hearing from anyone who has.
"Bryan B" wrote in message
...
Any suggestions for bedding plexiglass window to fiberglass deck
opening.
Polysulfide, Silicone, or another material?Which brand?

Thanks,

Bryan






James Johnson
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