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Author Topic:   Gel Coat Bubbles (Blisters)
Ray posted 10-01-2001 06:38 AM ET (US)   Profile for Ray   Send Email to Ray  
Just pulled my 25 Revenge from Lake Michigan this weedend (sad day). I have not painted the sides below the water line and as usual I get about 2 inches of slime that is very tough to remove. The bottom has interlux trilux and works fine. For the sides I used a power washer and Starbright hull cleaner. The next day I noticed many blisters all along the entire length of the boat where the scum line was. I poked one and it leaked brown water. I had planned to paint this area with interlux but do not know what to do now to prep it. Is this serious or just cosmetic? The bubbles are about 1/8 to 1/4 inch wide. Mooring site is Black River, South Haven, MI (sort of nasty water).
jimh posted 10-01-2001 07:36 AM ET (US)     Profile for jimh  Send Email to jimh     
This sounds like osmotic blistering. Many builders had problems with this, but I have not heard of many Whalers that have been affected by it.

You'll have six months (of winter) to let the boat dry out. That is the first step in the repair process. After that, it gets ugly.

The blisters are usually ground out and new gelcoat resin applied. In some cases of severe blistering, entire hulls have been stripped of their gelcoat, allowed to thoroughly dry out, sealed with epoxy topcoats, and then repainted.

jimh posted 10-01-2001 07:58 AM ET (US)     Profile for jimh  Send Email to jimh     
Also, see this thread:

acseatsri posted 10-01-2001 09:51 AM ET (US)     Profile for acseatsri  Send Email to acseatsri     
Everything you ever wanted to know about blisters- and lots you don't!

ghwillis posted 10-01-2001 02:45 PM ET (US)     Profile for ghwillis  Send Email to ghwillis     
try this thread. lots of useful information. I have noted similar on bottom of my modified Katama (1979 hull)

My general sense from the various articles is that unless done right, better not to do it at all.

LarrySherman posted 10-01-2001 05:28 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     

What did you poke, the bottom paint, or the gelcoat underneath? Take a good look with a bright flashlight and see whats going on.

What did you poke with?

How thick was the "scab" covering the blister?

What color was the liquid?

What did it smell like?

Ray posted 10-01-2001 09:05 PM ET (US)     Profile for Ray  Send Email to Ray     
I chased down the thread that JimH posted above and learned a lot but don't like what I learned.
Larry, The blisters are above the chine and below the water line. They appeared on the 2-3 inches that are below water but not bottom painted. I poked with my jack knife and found the skin very thin. The brown ooze that stinks came out. Sounds exactly like what was described in the above thread. What was wierd was that when I cleaned the slime off on Saturday with a pressure washer and starbright hull cleaner there were no blisters. The next day the small strip that was slime covered was now covered with blisters. It's like maybe the pressure washer forced water into the gelcoat or the acid in the hull cleaner reacted with the hull. At this point I am thinking of just putting bottom paint on that portion next spring and calling it ok. If I need to make a repair to prevent further damage then that's another story. Thanks for the help.
LarrySherman posted 10-01-2001 09:29 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
I think it was the change in atmospheric conditions, humidity and pressure, but I could be wrong. But yes, it does sound like blisters.

This is always a tough decision for the owner of a classic. I certianly understand the pain this causes.

When I first bought my boat, I had dreams of a pristine white gelcoated beauty. the reality is just slightly different. I have several different colors of gelcoat, and lots of cracks. I have my entire bottom coated in 2 layers of interlux epoxy barrier coat, with some west mixed in around the thru hulls. I have different pattern nonskid on the parts of the deck I rebuilt.

And do you know what?

Nobody but me notices. From 10 feet away I don't even notice. I realize now that I enjoy my boat much more for its utility, and my ability to fix it to the best of my abilities, than has some trophy I'd be afraid to use.

If it were me, I'd use a laser to make a line along the hull above the highest blister. Tape off above the line (both sides), sand away all the bad, dry with heat lamps and propane heaters for a few months. Good time to put a vaccume pump on her as well. Then, barrier coat the sides, or do the whole bottom if your up for it. Then make a bootstripe from the tape to the real waterline, and bottom paint the rest, overlapping the lower edge of the bootstripe. I always liked white/black/red. Very cool. Get the 14 inch high decals and you will have the coolest boat in the harbor.

and you also won't worry about blisters.

If you really want to fix the gelcoat to origional, let me know and I see if I can help.

LKS posted 10-01-2001 10:17 PM ET (US)     Profile for LKS  Send Email to LKS     
Unfortunately, blisters should not be ignored. If left unattended, they tend to worsen over time. The worse they get, the more moisture absorbed into the hull. More water absorbed = heavier boat, among other things. Speaking from experience, I'd suggest that you carefully check the rest of your hull below the waterline. Bottom paint does not prevent the formation of blisters. A barrier coat will help, but plain bottom paint does not protect against blisters. If you've got them along the waterline, it's likely there are more blisters on the hull bottom. Been there; I feel your pain! -- LKS
jimh posted 10-02-2001 09:14 AM ET (US)     Profile for jimh  Send Email to jimh     
This is very strange that the blister were not there after a summer in the water, then appeared overnight after the power washing.

Something strange is happening here. Maybe too much power in the power wash? Too much acid in the cleaning solution.?

Or is this normal that it would take 24 hours for the moisture in the hull to appear after a haul out?

Also, if you have gone to bottom paint, why not paint the hull sides that are in the water, too? It is not much more paint, and it avoids all the slime/fringe growth.

noswah posted 10-02-2001 10:41 AM ET (US)     Profile for noswah  Send Email to noswah     

I think it might be reasonable to assume that water from power washing could enter the hull. If you have a power washer with 2000 psi or more (some are 3500 psi)using a jet stream tip you can etch concrete and cut 2x4's in two. Might want to take a second look at chemicals to clean the hull, or get someone who knows the pros & cons of power washing.
lhg posted 10-02-2001 02:31 PM ET (US)     Profile for lhg    
Sounds like the pressure washer caused the problem. The gelcoat probably had absorbed a little moisture from being unprotected in the water all season, and the pressure drove it through and caused it to blister. As mentioned previously, gelcoat blistering is not a common problem with Whalers. In 33 years, I've never has a single one.
Ray posted 10-02-2001 09:58 PM ET (US)     Profile for Ray  Send Email to Ray     
I do suspect the pressure washer. It was only the 1200 psi model but we hit her good. I poked a couple more holes today with my pen knife and clear water came out of these. Guess I will visit West Marine tomorrow and pick up the book. By the way what is barrier coat? Also after a very careful inspection of the hull bottom there are no blisters on any of the bottom painted surfaces, only the unpainted side below water line. I plan to go with your suggestions Larry and sand, dry, repair, paint and stripe. One more thing. I pulled the screws from the deflector over the drain tube below the rear sump (25' Revenge) and water began to leak out of all screw holes???!!! The drain tube seems all intact and not rotted out at all. Yet there seems to be water in the foam in that area. I pulled the other caps off from the other 4 drain tubes and no water at all. Should I pull vacuum here in this area? And how does one do that?
LarrySherman posted 10-02-2001 10:20 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
I'm still not sure it is the pressure washer. The chemical reaction that occurs in a blister, and creates that nasty brow fluid, would not occur in 24hrs. If your getting clear water, then yes, the power washer, if not, than I think something else.

I mention this because there could be more or less going on here than meets the eye. Lets say your boat was awlgripped a few years back, and they extended the awl grip below the waterline. Then what you are seeing is paint blisters, which is common with 2 part polys used below the waterline.

Or a previous gelcoat repair could be the culprite.

Ray, a picture is worth ..., can you get your hands on a digital camera, take some pics, and mail them to me and the other interested/supporting members? I'd really like to see whats going on before my advice encourages you to pick up the grinder!

The problem Ray is that what you are describing presents some inconsistancies(sp):

1)Clear water from some blisters, brown water from others

2)Very thin shell on blister (this is good, in general, but in some cases blisters run DEEP).

Some more questions:

What year is your boat?

Has she been painted?

Are you the origional owner?

I post the info on the vaccume pump and thru hulls as links. And yes, there is water in your foam. But don't worry about it. If I were a betting man, I'd lay you $100 that there is not really a dry boat on this site.

I'll post links to that info too.

DIVE1, where are you?

LarrySherman posted 10-02-2001 11:29 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     

Drain Tubes and such:

Vaccume Pumps and such.

Ray posted 10-03-2001 11:04 PM ET (US)     Profile for Ray  Send Email to Ray     
Thanks Larry,
I'll get the camera this weekend and fire some pics to you and others. I picked up the blister repair manual at West Marine today but will not get to hasty yet with the grinding wheel. Right now I'm putting in a new water pump and thermostats.
Ray posted 10-06-2001 09:59 PM ET (US)     Profile for Ray  Send Email to Ray     
Talked to Randy at West Shore Marine (Saugatuck MI) this weekend. Randy grew up in the Whaler business with his folks. He told me that all boats that are left in the water without bottom paint will blister. He said simply grind off the bubbles and let it dry all winter then fill and barrier coat and bottom paint according to West Systems. I also told him that I removed all the under hull drain tube deflector caps and water leaked from only the very bottom one. He said that he would remove the drain tube and let it dry over the winter and replace it. He would not replace the other ones as they did not drip water. The boat is a 1985 and all drain tubes feel intact when you run your finger up from the outside.
bigz posted 10-07-2001 12:35 PM ET (US)     Profile for bigz    
Ray, you might want to glance at this information. need Acrobat pdf reader or you can get in a Word doc. here

I would recommend from experience replacing all the drain tubes at this juncture. The others will eventually fail.

Good luck Tom

LarrySherman posted 10-07-2001 06:26 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     

Tom is absolutly right. Get it done now, and don't ever worry about it again.


DCPeters posted 10-08-2001 12:32 AM ET (US)     Profile for DCPeters  Send Email to DCPeters     
I gotta say that I've never painted a boat bottom in my twenty years of having fiberglass boats. In in April, out in October. Never had a blister.

We power washed each fall. I had one boat ten years, so it wasn't as if I was lucky or buying new all the time (far from it).

I dont' agree the comment that all boats blister.

noswah posted 10-08-2001 08:14 AM ET (US)     Profile for noswah  Send Email to noswah     

I don't know if all boats blister (as someone suggested) but mine is a 73' 16/17 and has no blisters anywhere as far as I can tell. For those who have not painted or regelcoated the bottom, perhaps a good coat of wax that was installed was enough to protect your hull from power washing or the correct tip (fan spray) was what saved you from blisters.

I know the power of these washers. An airless spray painter 2000 psi to paint your home with will blow paint thru your skin and you will have to find a decompression chamber in 4 to 5 hours or loose your limb. I removed the paint off of my wife's new Camaro with one I had when I first got it.

If your going to use a pressure washer I would make sure you never sprayed head on. I would always want to spray at a 20 degree angle and use a fan spray. I can assure you you can cut a hole thru your hull with the right washer and tip. Just my thoughts.

DCPeters posted 10-09-2001 01:24 PM ET (US)     Profile for DCPeters  Send Email to DCPeters     
I think you may have it, noswah. I agree with your conclusion. Of course, it was fresh water too (Lk Ontario)so no barnacles here...

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