Painted teak transom of f/g IG36

I have a problem with sporadic paint bubbling on the teak transom clinker type paneling applied over the fiberglass.Like GBs, the teak is varnished by the builders. Some work shy PO painted it.
There were sporadic bubbles when I bought it 7 years ago. About 5 years ago I had it repainted, it was thoroughly sanded and prepared, though the first finish coat went "flat" due to ? a moist overnight. It was resanded, and repainted, 2 pack. The boat was in a shed for osmosis work etc, the transom faced the opening of the shed. It is possible the transom got light rain spray, but for that to be the cause, it had to get wet both times it was painted, which requires an unhappy coincidence.
I wanted to return to varnish, advice was that once painted, it is near impossible to get all the paint off, so new paint. The repaint bubbled in short time. The bubbles don`t change or burst, the only open one was cut open for exploration, it seemed to hold water.
I don`t rule out trying to get the paint off and varnishing again. Alternatively repainting, maybe with a durable plastic domestic outdoor paint to allow moisture through(relying on a house reno project experience where the specialist builder engaged to fix damp issues said it was ok to paint the fresh set render with plastic paint but NOT with an oil based paint,worked out fine).
I would appreciate similar experiences,thoughts on cause,and remedies. Especially on removing the paint and going back to varnish.

If your wanting to keep it painted, I would remove all the paint, wood it.
Let it dry good.
Prime it with an latex primer, I like Zinsser Bullseye 123 made by Rustoleum here in the USA.
Then use a gloss exterior acrylic house paint, which will breathe water vapor. Acrylic latex paints seem to hold up well on vertical surfaces compared to flat ones. My hull paint is acrylic latex and when was 7 years old looked like new. Of course that type paint never has a mirror like shine, but has a semigloss to satin type look even if sold as a gloss paint.

Question is why is water soaking in behind the paint, does the teak wood have a crack, somehow rain is flowing back behind the wood?

Is the transom hollow? Internal condensation can cause bubbles/blistering from what we've been told. We have a similar problem on the fashion plates on Hobo which are hollow, water tight and painted with a 2 part. I've talked to several yards with Huckins Yachts being the most recent. Their solution was to refinish and add a small vent. For the time being we're living with it but have added it to the list.

I think it's pretty hard to keep paint on teak . The oil in teak is always trying to come to the top and it wants to push the finish off . Maybe if the first couple coats of primer are thinned way down like you do when varnishing that might help . When varnishing teak I've always tried to get the oil to lay down long enough for the first coat to penetrate good and dry before the oil has time to push it off . I usually clean raw teak with acetone first and then get a thin coat on right away , but I've never painted teak . This is just what I do .I can't claim that it's the right way but so far it has worked for me.

When any wood gets wet under any paint, it wants to peel or bubble up.

Certainly an oil paint is probably worse though since it is more waterproof than an acrylic latex which supposedly, water vapor moves through the paint. Idea being the wood stays drier under the paint.
Unless the wood is getting flooded with rainwater or condensation under the paint on the backside of the wood from wood cracks or a water collecting space.

I have a treated wood rub rail I made 10 years ago. Where two ends meet, I dd not seal the end grain. So rain wicks in there, the wood stays wet, and the paint does not like to stay on the wood in that area. I need to remove the SS rub rail section, and unscrew the 5 foot piece of wood rub rail, let it dry, then seal the end grain. Someday.

Thanks guys.
Pack Mule, I now remember years back painting a teak garden seat, oil primer, oil undercoat,oil topcoat. Great rustic look, of peeling paint.
Not sure what`s inside the transom between the inner and outer f/g panels. I have the name boards off now to repaint the letters and revarnish. Water could wick down the attachment screws, to the teak overlay,even inside the transom where the screws extend. I taped the screwholes when I removed the boards, when I refit them I`ll use a non silicone non 5200/sikaflex brown color caulk(has to be kept un-doable), to seal the screws heads, and screw shafts where they enter the teak overlay and transom.
Larry,adding vents to the transom is a good idea, I could do that as part of the refinish. My preference remains varnished teak, the thickness of the teak overlay will decide that.
sdowney, thanks for confirming my thoughts on paint choice,that makes sense,moisture permeable house paint it is if I repaint.

Hi Bruce,

Late last year when Malagari was on the slip, I stripped off the old varnish (not too bad but some areas were flaking) - I used a heat gun and scraper - its surprising how big the transom is when you are kneeling on the swim platform.

I wiped the bare teak with acetone and applied umpteen coats of varnish - I had taken the two steps and name plates off prior and they got the same treatment. It looks great - so great that I had a cover made to keep it that way.

George

Brisyboy said:

Hi Bruce,

Late last year when Malagari was on the slip, I stripped off the old varnish (not too bad but some areas were flaking) - I used a heat gun and scraper - its surprising how big the transom is when you are kneeling on the swim platform.

I wiped the bare teak with acetone and applied umpteen coats of varnish - I had taken the two steps and name plates off prior and they got the same treatment. It looks great - so great that I had a cover made to keep it that way.

George

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I`m envious, Malagari`s transom must look good. To varnish the paint has to go, you are lucky no one painted her butt.
Did you get any sense of the thickness of the teak planking across the transom?
btw, I once heard the word "tuck" used instead of transom. Anyone heard that?

BruceK said:

I`m envious, Malagari`s transom must look good. To varnish the paint has to go, you are lucky no one painted her butt.
Did you get any sense of the thickness of the teak planking across the transom?
btw, I once heard the word "tuck" used instead of transom. Anyone heard that?

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Bruce - hard to judge thickness, but it could be 20mm(ish)

I`d be keen to see how paint stripper works - esp as it could be hosed off after the stripper works without damaging any other paint or gelcoat

Brisyboy said:

Bruce - hard to judge thickness, but it could be 20mm(ish)

I`d be keen to see how paint stripper works - esp as it could be hosed off after the stripper works without damaging any other paint or gelcoat

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George,I used strippers(for paint removal )until TF suggested the heat gun(around $20 at Bunnings)and scraper method I used ons my name & port boards.The chemicals are nasty to use, messy, needing gloves,neutralizing etc.
Does heat work on 2 pack? Why not, paint bubbles nicely with moisture, but lots of sanding after.
Any ideas on a varnish? Cetol TGL Gloss Plus is my choice.

If you do plan to paint anyway, I would remove all the wood and refinish the fibreglass then paint it. With a good two-part and some maintenance it should last for years without having to do it again. I would be surprised if this solution was more work than restoring the old painted teak.

My GB 32 never had a varnished transom and every year when I did my maintenance I was VERY glad it didn't. I don't think it looked bad either, never missed it.

Xsbank said:

If you do plan to paint anyway, I would remove all the wood and refinish the fibreglass then paint it. With a good two-part and some maintenance it should last for years without having to do it again. I would be surprised if this solution was more work than restoring the old painted teak....

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Thanks Xsbank, good alternative thought. Return to varnish makes work,(probably why it got painted),then I`d need a drop over canvas cover...it never ends...

Aw shucks...you're welcome!