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new to me 84 mac 22 (had a 72 version over 10 yrs ago). Got it on boat stand and found a blister on the bottom, took a small chisel and screwdriver and opened it up a little (about 2" long). lied on the ground and pushed my palm against the surrounding area, there's a little bit of creaking sound, like there is a void in there. what is my next step? should I try to open it up more? how would I do that, will an oscillating tool work better?

I'm not a fiberglass expert. There are lots of Youtube videos on that stuff.

My guess is that you want to chip away most of the bad stuff with voids and fill it with something.

I'd say it's a bad one. Looks like it's down to raw glass. Easy to fix, though. Heat it up with a hot-air gun to disperse any remaining water. Then, after using all my previously stated bodily protections (see my other postings about fiberglass work), I'd grind out the area to remove any loose fibers and get to the full extent of the margins, then use chopped glass and epoxy resin to bring it to near the surface (you can use cabosil to thicken the resin so it doesn't drip). Finish it off with a marine-grade gelcoat that has a wax additive (without the wax it will remain sticky and never really harden). Sand, polish and buff to bring it flat and shiny.

Hi Sailor1!

Glad you’re here!
Sorry about the blister!
From appearances it’s something to fix as it’s a layer or two deep into the fiberglass.
Kmclemore is spot on in his recommendations.
Be careful with the grinding as you want to leave the good stuff and only take away the material that has become separated.

The only things I’d suggest is to tap around and see if there are more blisters that need to be addressed so you can deal with them all while you’re at it and to apply an at least two epoxy barrier paint coating on the entire bottom up to the waterline stripes after stripping off any of what looks like old ablative coating. That way you can potentially stop further blisters from forming in the future.

It looks like at sometime in the past a potential epoxy paint may have been applied (the teal ish color) but it has been worn away as has what was an ablative paint of some prior vintage. Cleaning it up with a power washer and/or sanding will give you a fresh surface to work with.

Good you found it now and can address it! You got this!

Best Regards,
Over Easy

Or.. just leave it.. and get a bigger Bilge Pump...


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Hi Adudinsk!

Q: If a bilge pump could pump bilge how big a bilge pump would be needed to pump that bilge?

Best Regards,
Over Easy

Hmm... I will have to ChatGPT that one...

LOL




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