Blister/Bottom Job Questions

[Finn]

I have a '86 Catalina 27 that I want to do a bottom job on. It already has some sort of blue bottom paint on it. The bottom also has some gel coat blisters that I do not want to address at this time as well as a paint blisters that I know of and maybe a few more that I do want to take care of. My questions are, (since this is the first time of doing this myself) .. 1. how can I tell a paint blister from the other kinds of blisters. I don't want to open up the gel coat blisters but I do want to take care of the paint blisters. How do I do this? 2. After I open up the paint blisters and there is bare gel coat underneath, what do I use underneath the paint blisters? 3. How can I tell if it is an ablative paint or an modified epoxy paint ( for compatability reasons ) and 4. If the bottom is an ablative paint, is it possible to change it to an epoxy paint and how? Thanks .. Any advise is greatly appreciated.

 

[Joe Ford]

Bottom work

1. Once you have the boat out of the water you will have no trouble telling which one is which. Have the boatyard tech inspect and advise you before you start working. The paint that is blistered or flaking should be easy to remove. 2. On bare gel coat, rough the area with 80-100 grit then and apply a two part epoxy primer. There are time considerations so read the directions and consult with the paint dealer.#3 & #4 consult with boatyard tech or paint expert at marine store.

 

[Joe Luciano]

Blisters

Other things you might consider:1. If the blisters are under the gel coat, smaller than a quarter and not too many, suggest you leave them alone or monitor them over several seasons.2. It will be obvious when you begin sanding if the blisters are paint blisters or gelcoat blisters. If you only sand very small areas down to the gelcoat, I wouldn't worry much about applying a special gel coat primer prior to bottom painting. For the larger areas, you can buy a primer made for this purpose. West Marine sells products like this.3. Ablative paints are compatible with epoxy paints as long as they are sanded to remove loose paint and give the new paint a good base to adhere to. Often it is a good idea to use a wire wheel at the water line to buff off the old paint.Also,you can find out what paint was used prior if the former owner had the work done at a boat yard. Often the yards keep records of paints applied if they did the work. I personally like the epoxies like Woolsey's Neptune which are tough and hold up well to brushing for a couple of seasons.Good luck!