Can I put VC-17 over hard bottom paint?

[Finallybuyingaboat]

I am entirely redoing a shark 24 and want to put VC-17 on the hull. I have sanded off the yucky black antifoulign paint and have gotten down to a hard paint layer(s). I am not sure if I can apply VC-17 directly on to this. The paint is a copper/gold color, and some areas where I have sanded through this copper/gold layer there is a coat of a hard blue paint showing through. I have no idea what brand of paint this is, but can I chance painting VC-17 right on this? Any other ideas for a really fast bottom paint for freshwater that does not require me to sand right down to the hull. I am not even sure if I could sand down this hard paint, it is EXTREMELY difficult to sand away. Worse case, is there a primer I could put on between the existing paint and the VC-17?

Also, any other really fast bottom paint alternatives worth looking at? Any new Teflon paints out there anyone is aware of?

Thanks

[camaraderie]

Yes you can. Here's the data from Interlux:

	PREVIOUSLY PAINTED SURFACES: with VC 17m and: with VC 17m Extra with Biolux: Surface must be clean and dry prior to application of VC 17m Extra with Biolux. Sand areas that are loose or flaking with 320 grade (grit) paper. Clean with Special Thinner 216. with conventional antifouling paint: Removal is best but if this is not possible, start sanding with 80 grade (grit) paper and progressively sand with finer grades until the final sanding with 320 grade (grit). Remove sanding residue. BARE FIBERGLASS: Begin by scrubbing well using soap and water and a stiff brush. Rinse with fresh water. Wipe with Fiberglass Solvent Wash 202. Sand with 320 grade (grit) paper. Wipe clean. BARE WOOD: Wipe clean. Sand surface, wipe clean. Apply 3-4 coats of VC Tar2. STEEL/LEAD: (Keels & Hulls) Blast to near white metal surface (Sa 2½). Apply 3-4 coats of VC Tar2.
Method	Apply 2-3 coats on the area to be coated per season. Do not sand between coats of VC 17m Extra with Biolux.
Hints	Mixing Pour the powder (stored under the plastic hat) into the can. Stir or shake thoroughly. Thinner V172 Airless Spray Electric Airless Spray: Pressure: Full. Tip Size: 1.5-1.8 mm/60-70 thou. If spraying in hot, dry conditions or outside with wind, you can add VC 17m Thinner to VC 17m Extra with Biolux to slow down the dry time during application. Add up to 15% by volume. Spraying too far from the hull will cause dry spraying which will result in poor adhesion and negatively affect the antifouling performance of the product. Brush Do not brush apply. Roller Use a short nap roller. Add V172 up to 15% should VC 17m Extra with Biolux be drying too quickly for application. Put just enough paint to fill the roller in the roller tray and put the lid back on the can. Other Surfaces previously painted with VC 17m Extra with Biolux do not need to be sanded. Performance of the paint relies directly on the care taken in surface preparation, the application technique, and the number of coats applied. VC 17m Extra with Biolux is a copper color at application.
Some Important Points	It takes several weeks of immersion to develop final color. It may not change color above the true waterline. Product temperature should be minimum 10°C/50°F and maximum 32°C/90°F. Ambient temperature should be minimum 7°C/45°F and maximum 35°C/95°F. Substrate temperature should be minimum 7°C/45°F and maximum 35°C/95°F.
Compatibility/Substrates	Apply to clean, dry, properly prepared surfaces only. Bare surfaces must be sanded. Do not apply VC 17m Extra with Biolux over graphite antifoulings. Do not apply over soft antifouling paints. Do not apply VC 17m Extra with Biolux over aluminum.
Number of Coats	2-3

[sailaway21]

Here is some more information from International. Note that, if you do not remove all other anti-fouling paint, you'll need to use a primer. PrimeKote, if I recall correctly. VC-17 isn't compatible with other anti-fouling paints.
http://www.yachtpaint.com/USA/hotlinks/compat.pdf

Usually the easiest way to determine if you have a compatibility issue is to take some of the solvent for the paint you wish to apply new and try that solvent on the old coating. If you can rub off paint with the solvent, you're going to have a problem with the new paint. Either strip or prime, with stripping being the most desirable if the most arduous.

[GreatWhite]

I redid the bottom of my Shark last spring too! I took of the old soft antifouling paint (not sure what it was but it was reddish). I used a scraper and the palm sander with 80 moving to 180 grit (no other sanders needed - definitely keep the belt sander away!)
I used a layer interlux interprotect before adding the vc17 (mostly because I went through the gel coat in a couple of places), it might have been over kill but after a year in fresh water, the vc17 still looked great!

Maybe you could the Interprotect as a primer over the hard paint on your hull. I also used the Interlux 202 thinner to clean after sanding.

I bough four cans of vc17 put 3 on for the fist 2 coats, and saved the 4th for the haulout this year and it seemed unneccessary.

Good luck to you.