Purple-black blisters

[llldks]

On the underside of the flybridge overhang on a 1972 53MY, which has been repainted by PO, I develop a purple- black blister, usually during the winter months. In the past, I have broken the blister, ground out the area with a dremel, and filled the void with West epoxy after a few days. This appears to be a chemical reaction of some sort rather than rotten core. This year the discoloration reappeared in the repaired area. Has anyone had this problem? Any ideas as to how to treat area prior to repair?

 

[SEVEN]

Is this bleeding thru the paint?

 

[bigbill]

does it smell like resin? i had a blister on my transom that would bleed when opened, it was uncured resin. took about a week of wiping it with acetone each day till it quit

 

[34Hatt]

The black is the primer that Hatteras put in the mold after the gel coat so you wouldn't see light thru the glass. It seems that pocket of air in it can cause the blister and it always seems to happen in the cold months.

 

[llldks]

It does not smell like the blisters on the hull. It does bleed through the paint and smears when rubbed. I would have hoped that after 46 years all the air bubbles would have migrated, but maybe not. Will grind out area again, leave it exposed for awhile and then refill. Would there be any point in treating it with acetone or something else???

 

[Cricket]

Think I would grind it some more, hit it with the heat gun multiple times, wait a few days at least to see if there's additional fluid.
For the repair build it up with some biax cloth (1200 or 1700) using epoxy (West, etc).
Fair, prime and paint.
Had a similar situation twice, on the transom and side of the cabin.