Old Grady Bottom Paint

[sigp220in45]

I have a 1988 Grady White 24 Offshore that needs to have the bottom painted. Currently there is a heavy black very rough black paint over a blue paint and then I guess the boat bottom which is white.
Should I sand off all the paint to the white bottom, do I need a special primer before painting of just apply the bottom paint I have purchased. I have an ablative paint that is good for the area I have my boat located.

 

[GWL139]

Best bet imho is to find a reputable blasting company in your area to remove the 32 years worth of paint, barrier coat the hull, then repaint with a good ablative bottom paint...

 

[leeccoll]

If you decide to tackle it yourself, here is what the local shop did to remove my bottom paint last December.

Use a paint scraper carefully until the white gel coat starts to appear
80 Grit Sandpaper
320 Grit Sandpaper
600 Grit Sandpaper

Attaching a link for ya. Good luck!

228G Bottom Paint Removal

Decided last fall to splurge and have my bottom paint removed on my 1987 228 hull. It's been in the shop for about a month, and stopped in for a peek today. Amazing transformation so far. My Venture cheapo trailer had chewed up the strakes down to the fiberglass in areas, and the keel also was...

www.greatgrady.com

 

[Islander268GW]

If you want to get by another season, you could always pressure wash and use a one season paint like CPP from west marine.

Use caution sanding yourself...it will no doubt be a dusty mess and you'll want to ensure a proper respirator given the toxicity of these paints.

If you do sand all the way down, you will want a layer of primer below the paint for best adhesion. This is one of those jobs that sounds well worth the money to have someone else do it!

 

[sigp220in45]

Best bet imho is to find a reputable blasting company in your area to remove the 32 years worth of paint, barrier coat the hull, then repaint with a good ablative bottom paint...

Since I have plenty of time on my hands during this time, I have been working on the boat. Installed a remanufactured windlass, removed and refinished all if the teak, installed a new water pump, repaired the trim controls and cleaned the whole ship stem to stern. As it appears I still have plenty of time I have taken on sanding the bottom myself. I use 50 grit to get the heavy black crap off and then 80 grit to get to the gel coat. It is going to take a good long time to do. I read a lot about this and am still a bit confused regarding the painting of the bottom. Do I just paint with a quality ablative bottom paint or need I put down a base or primer coat? I ask this as the boat has the heavy black paint over a blue paint and then the gel. Is the blue paint the an older bottom paint that was painted over?

 

[DennisG01]

As it appears I still have plenty of time I have taken on sanding the bottom myself. I use 50 grit to get the heavy black crap off and then 80 grit to get to the gel coat.

Wait... your first post was an hour and half ago. So in 90 minutes you went from "asking" about what to do... to already doing some of it? What was the purpose of asking?

The blue is simply another color of bottom paint - it is not a barrier coat. If you're then seeing normal looking gelcoat, then it does not have a barrier coat under the blue, either. Chances are, you really don't need a barrier coat if everything looks good - if it ain't go blisters by now...

But, it certainly can't hurt to do a barrier coat and that would be "best practice". I would say, though, that since you are physically sanding (and no doubt will get into the gel) - it's pretty much a requirement to do the barrier coat. Just make sure to read and follow the directions.

 

[seasick]

I guess 90 minutes is better than the folks who post what they did and THEN ask if that action was appropriate.

OK now my two cents.
If the paint looks like a heavy hard coat, it is probably not ablative. In that case it probably can be painted with either a new coat of hard or an ablative. You can not apply hard coats on ablative. To test, just take a wet clean rag and wipe a section hard. Use some elbow grease. Look at the rag. If is whatever color the bottom paint is, that paint is probably ablative, This test doesn't work very well if you have already sanded!
Other than smooth out the old paint, there is not a real need to remove it all. Just remove chipping or peeling paint. Of course if you want to sand off everything, go ahead but be aware that you will have a lot more work ahead, both removing AND refinishing. If indeed you do sand down to the gel coat, you will probably also remove some get coat. It's really hard not to. In that case an epoxy primer coat is strongly encouraged followed by anti-fouling paint ' As to the two colors, many owners will have the bottom color changed for each repainting. That way, you can see where and if the latest layer have worn off. Blue first followed by black? Yup when you see blue spots the newest paint is worn away.

 

[sigp220in45]

Your advice is the best so far and is appreciated..Please understand, I only just started sanding on one side and have only sanded about 6 feet so far and reached the white gel coat and stopped. As of yet I have left the bottom untouched. I was afraid I had already sanded too far.
Your answers have reassured me I am doing it correctly.It will certainly save me time if I only have to smooth things before painting. I did not want to get too much done before finding out I was doing something wrong. Sorry for the confusion. I have saved the bottom paint as my last project in restoring this beast to its original beauty. She will be almost pristine when I am finished. Thank you.

 

[DennisG01]

OK, gotcha. So, yeah, if you're just looking to get things smoothed up a bit, then definitely don't sand too far. But I would try and get it at least to a point where the blue is thin enough that you can check for blisters. An occasional, small one here or there is no big deal, though. But I gotta admit, if I was sanding things that far, it wouldn't be that much more work to get it all off so I could barrier coat it.

Blisters... how long has it been since the boat was in the water and how long was the boat in the water? And, how long will the boat stay in the water in the future (and where)?

 

[Fishtales]

I'd have it blasted. Who knows what mix of stuff is on that hull. Barrier coat and 2 coats of ablative paint.

 

[seasick]

On a hull that is vintage 1988, you either have blisters or never will
Sometimes to be able to sleep better at night, it is better to not look for issues that may not be a serious issue ( my opinion) If there were serious blister issues, I think you would have seen them already.
In addition, you do not need to sand off every little spot of paint. Your goal is a smooth hull with no loose paint.
Now if you want to do a super long lasting job, a barrier coat is the ultimate 'underwear') .
Barrier coat is a misnomer too. It will be barrier COATS, 2 to 4 depending on the product selected, followed by two or three coats( on water line) of anti fouling paint. Don't skip the step of cleaning the sanded hull. Follow the advice of the paint manufacturer.

 

[SkunkBoat]

I've used gel bottom paint stripper on a transom before. Worked pretty good. Brush it on, wait, scrape off paint( get a real paint scraper at Home Depot)
Don't remember the brand name but it smelled like orange, water cleanup, no dust.
Took the bulk of the decades old bottom paint off. Then sanded it clean and did Bottomkote epoxy and then new bottom paint.
I just did the transom area as part of rebuilding it with pourable Carbon-Core.

I think I would pay to soda blast if I wanted to do the whole thing down to gelcoat.
If you just want to take down a few layers and repaint with ablative, then its an option.
Way better than sanding.

 

[seasick]

Sounds like the citrus paint remover. I tried some recently as an experiment on Pettit water based paint and to be honest, it didn't work well at all. I tried different times but none seemed to make a big difference. I will admit that it was fairly cool when I did the tests. I may try it again when it gets warmer and I am able to get to that boat.

 

[DennisG01]

One thing that can help with paint strippers is covering the stripper with plastic after applying it on the hull.

 

[seasick]

That option is on my list whenever I get to the boat.
The longer time test did result in the gel drying out.

There is nothing like the old methylene chloride. Unfortunately it caused cancer and heart disease It did work magic though.
Kind of like the lead based paints, phosphate based detergents and chromium based primers.
There was a lot of things we used that could kill us.

 

[SkunkBoat]

Sounds like the citrus paint remover. I tried some recently as an experiment on Pettit water based paint and to be honest, it didn't work well at all. I tried different times but none seemed to make a big difference. I will admit that it was fairly cool when I did the tests. I may try it again when it gets warmer and I am able to get to that boat.

You need one of these. Once its softened, this scrapes it off. If the paint is 10 layers thick it will take multiple passes but its way better than sanding.

 

[seasick]

I have used that type of scraper. It is a good idea to slightly round the tips of the scraper blade. If left sharp, it is easier to gouge the gel coat That said, I really don't like to use them. For old builtup hard paint, they can be useful, but they don't work as well on thinner ablatives.