Mac 25 bottom issue

Grumps

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Mar 4, 2021
71
Macgregor 25 Trailer
I bought a 1983 Mac 25. The previous owner had it about a year. He left it in the water (fresh) because he believed it had bottom paint. I don’t think it does. The are a lot of little blisters and some places where the gel coat has popped off. I bought this boat because it is on a trailer and I wanted a project. So, I am wanting opinions on if I should remove the gel coat to the water line or just sand it smooth and fill the potholes? I am going to use a barrier coat and then Coppercoat the bottom. I’ll post a pic of some of the blister/holes.
 

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Jan 11, 2014
13,064
Sabre 362 113 Fair Haven, NY
Welcome to SBO.

Because there is blue showing through the what was white paint, I think the barrier coat failed and that caused the blisters.

Removing the white paint will give you a better idea of the problem. If they are gelcoat blisters, they will be under the gel coat. Pop a few of the blisters to see what's under them.
 

Grumps

.
Mar 4, 2021
71
Macgregor 25 Trailer
Thanks. So, do you think the white coating is actually a barrier coat and not the gel coat? I’m not sure what the blue color is under it.
 
Jan 11, 2014
13,064
Sabre 362 113 Fair Haven, NY
Thanks. So, do you think the white coating is actually a barrier coat and not the gel coat? I’m not sure what the blue color is under it.
Yes. The blue is gelcoat. It is a stripe that runs along the waterline aka boot stripe. In fresh water boat owners often raise the waterline because fresh water is less dense than salt water and boats will sit lower in the water by an inch or so.

It might also be a build up of hard bottom paint. Start removing it to see what's there. Don't breathe the dust!
 
Jan 19, 2010
12,625
Hobie 16 & Rhodes 22 Skeeter Charleston
Removing old paint can be a real pain... but there are some tricks that can shorten the job. Let chemistry be your friend here.

HOMEMADE PEEL-AWAY:
Take a 5 lb bag of garden lime (Lowes) and about four cups of potassium (or sodium) hydroxide ... canning lye is a good source or drain-o. Put the lime and lye in a 5 gallon PVC bucket and add just enough water (with stirring) to get a melted peanut butter consistancy. Use a roller on a pole to role this onto the bottom paint and let it dry hard (over night). Pressure wash and 90% of the paint will flake off. If you want to be environmentally friendly, lay down an old sheet under the boat before you pressure wash and the sheet will filter the pressure wash water and collect the flakes of bottom paint. Ball up the sheet and dispose of it in a suitable way.

DO NOT GET THIS STUFF IN YOUR EYES! Wear goggles.

I've done this with several boats. There are always one or two spots where the paint just adheres and won't peel off with this trick. So I paint those spots with citrus strip (also Lowes) and scrape off those last few spots with a hand scrapper. Sometimes a second run with the peel-away helps but usually those tough spots need a more agressive formulation.

At this point you will have a nice clean bottom with only gel coat. Pop any blisters if they are there... lighly sand and presssure wash again. Fill in the popped blisters, gouges and dings with thickened epoxy (I like Jamestwon Distributors). Sand the repairs smooth and wash one more time. Let it dry a week and then put two or more coats of epoxy barrier coat over the bottom. If you want to save a little money on barrier coat, James T Davis or Sherwin Williams paint stores carry epoxy barrier coat paint designed for swimming pools. I have used it on two of my previous boats with absolutly no problems. It is cheaper than anything with the word Marine on the label and also has UV inhibitors already mixed in.

Hope this saves you some elbow greace.
 

Grumps

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Mar 4, 2021
71
Macgregor 25 Trailer
Thanks. So, you also think the white stuff that is popping off is a bottom paint and not gel coat?
 

Grumps

.
Mar 4, 2021
71
Macgregor 25 Trailer
Thanks. I’ll dig into it and see what is there. I currently have the rudder ground down and drying out. It had some nasty blisters and it was waterlogged. Should be almost ready for new fiberglass.
 
Jan 19, 2010
12,625
Hobie 16 & Rhodes 22 Skeeter Charleston
How is your keel. I used to have the baby sister of that boat (Mac 22-2). The keel on a Mac 22 was 600 lbs. I'm guessing the Mac 25 keel will be a PITA to remove and to move around safely.
 

Grumps

.
Mar 4, 2021
71
Macgregor 25 Trailer
How is your keel. I used to have the baby sister of that boat (Mac 22-2). The keel on a Mac 22 was 600 lbs. I'm guessing the Mac 25 keel will be a PITA to remove and to move around safely.
I haven’t removed it yet. I plan on doing that soon and sandblasting it at some point. I’m going to hoist the boat up and pull the keel out on the trailer...or so I think. Then I hope to hook it to a hoist to move it around. I think it is 650 lbs.
 
Jan 19, 2010
12,625
Hobie 16 & Rhodes 22 Skeeter Charleston
I haven’t removed it yet. I plan on doing that soon and sandblasting it at some point. I’m going to hoist the boat up and pull the keel out on the trailer...or so I think. Then I hope to hook it to a hoist to move it around. I think it is 650 lbs.
I sand blasted a keel on a Balboa 26 (1200 pounds). I bought a used engine hoist on Craig's List and then sold the hoist on CL when I was done using it. If that keel falls flat, you will have a heck of a hard time getting it off of the ground. I built a cradle and lifted the cradle up to the keel using jacks. Then moved the keel to the hoist once using the cradle once I lowered the cradle. Pics make more sense than my description.

image-1.jpg
Keel-oorah.jpg
Ready.jpg
In Position.jpg
 

Grumps

.
Mar 4, 2021
71
Macgregor 25 Trailer
I haven’t removed it yet. I plan on doing that soon and sandblasting it at some point. I’m going to hoist the boat up and pull the keel out on the trailer...or so I think. Then I hope to hook it to a hoist to move it around. I think it is 650 lbs.
I sand blasted a keel on a Balboa 26 (1200 pounds). I bought a used engine hoist on Craig's List and then sold the hoist on CL when I was done using it. If that keel falls flat, you will have a heck of a hard time getting it off of the ground. I built a cradle and lifted the cradle up to the keel using jacks. Then moved the keel to the hoist once using the cradle once I lowered the cradle. Pics make more sense than my description.

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I removed my keel. Looks to be in really good shape. I used the trailer to hold it and slide it from under the lifted boat. Now to sand blast and refinish.