is a barrier coat needed?

[seakat]

I am buying a 1999 SeaCraft23. The bottom paint scrapes off easily and is not adhered well. I am going to remove the bottom paint and prep the bottom. Do I, should I need to put a barrier coat on her before the bottom paint?

[pelican]

usually what causes the paint to peel - poor prep

fiberglass hulls require dewaxing and scuff sanding,prior to painting/coating
this process is often skipped - end result,paint peels and pops off


now:

if you're having the boat blasted:

after it's blasted ,it's gonna require a finish sand,to remove any remaining paint residue.

after that,solvent wash,and barrier coat it

do the barrier coat like this:
start with grey,and alternate coats of grey and white - this assures complete coverage
you want that barrier coat to be 10m thick - use a matchbook cover as a guide

number of coats means nothing,thickness does - one coat of barrier does nothing...

[seakat]

What I want to know, is this, Can I scuff up the thin layer that is on there and get by with just bottom paint? Would a "99 SeaCraft23 be expected to absorb water or develop blisters?

[tautog_33]

Seakat do you leave boat on a mooring or slip? If so then the bottom paint should be removed by either a blasting media, sanded with orbital sander, or paint stripper. If you use trailer only no need for barrier coat waste of money. Also, yes you could just scuff up and recoat bottom but you may not be happy with the results. I just sanded 3-4 coats off my 20 SF was a PIA I now have a clean bottom and going to use epoxy trailer boat paint made by Blue Water Marine Paints. Hope this helps.

[WildBill]

It is always going to depend what is on there now. That's what determines what you have to do. You can go to any of the bottom paint companies web sites and find out how or if you need to remove, prime, scuff or paint over with a compatible material. I thought the interlux site with their blog was very informative.

goodluck bill

[Fr. Frank]

I spent many years managing marinas in the south. I echo that the previous paint is probably peeling/flaking off because of poor prep. The other reason it can flake of if it was an ablative paint that spent a lot of time in the air before being initially immersed - like months.

Regardless of the cause of the problem, the old paint has to be removed to get new paint to adhere properly, AND it needs a good barrier coat if you're going to keep the boat in the water using an ablative paint like Interlux Micron or Petit Horizons. If you're going to use a hard bottom paint like Interlux Ultra or Petit Trinidad, simply removing the old paint and sanding the bare bottom with 80-120 grit sandpaper will provide you with excellent adhesion and durability.

If you intend to keep the boat on a trailer, you need a hard bottom paint that uses biocide leaching for antifouling, as well as being resistant to wearing away from launching and reloading onto the trailer.