Prepping to reapplying bottom paint.

[jcruise201]

I hope sail boat community will accept this new thread. I have read this website for a couple of years for information on bottom paints for my previous boat and there has been useful information that was factual and easily applied to my last boat project. I am a power boater and will be preparing to repaint the bottom of my newer used small cruiser. I cannot seem to get the straight information from the sources I have talked to at the marinas.
My question is the bottom paint on the boat I purchased in the fall needs to be replaced. The bottom paint is painted to the outdrive, as I scrapped the two inch boarder from the gimble housing the bottom paint scrapped off easily. The bearier coat was a little more difficult to remove. I was able to remove it with a sharp putty knife.
Here is my question; Do I need to remove the bearier coating if it is adhearing well and not flaking off the boat?
My thoughts are to apply a fresh coating of bearier coating after I remove all the bottom paint and use the appropriate chemical to wash the surface, to remove loose dust, etc. and apply a fresh bearier coating and bottom paint as usual.
Your Input Is Appreciated.

[zz4gta]

What barrier coat are you using? Follow their directions on the can, exactly.

I'd be suspicious of a barrier coat that can be removed with a putty knife. Most barriers need to be sanded off.

[SlowButSteady]

I'm with zz4gta. If the barrier coat can be scraped off it probably wasn't applied properly in the first place (unless your putty knife is actually chipping away at the gel coat underneath the barrier coat). It sounds like you may have to take it down to bare gel coat (it there is any), apply barrier coating, and apply bottom paint on top of that.

[Sailormon6]

Originally Posted by jcruise201

Here is my question; Do I need to remove the bearier coating if it is adhearing well and not flaking off the boat?

No. If the existing barrier coat is adhering well, leave it alone. If, however, you damage the barrier coat because you have been too aggressive in removing the old antifouling paint, then you might have to remove the barrier coat. My suggestion is to not remove all the old antifouling paint. I don't know what the condition of your existing antifouling paint is, but I would suggest that you wet sand it until it's reasonably smooth, and then apply fresh antifouling paint over it, following the manufacturer's instructions on the can. Unless the condition is really bad, with lots of peeling old paint, there's no need to remove all the old antifouling. Just sand it smooth and paint over it.

Although barrier coat can be applied to other surfaces than gelcoat, it is designed to adhere best to gelcoat. If your outdrive is aluminum, barrier paint might not adhere well to aluminum, and that could account for it being easily removable from the outdrive. Nevertheless, it might still be adhering well to the gelcoated hull. Unless you have some reason to believe it is not adhering well to the hull, I'd leave the barrier coat alone.

[jcruise201]

Thanks for the feedback from all of you.

The putty knife I used I sharpened with a file. So the barrier coat was adhearing extremely well. It took real effort to remove it. The bottom paint on the other hand seemed to flake off easily.

[Brent Swain]

a fisherman told me he boosted the copper content of his bottom paint by adding finely ground copper sulfate from the garden shop. Said it helped a lot.

[benjmin]

Pictures would help show us what you are up against.

[jcruise201]

Thanks regarding the copper additive. However, I read in Boat US that copper may become a restricted element in the next 6 to 10 years. Apparently it has negatively affected the shoreline marine environment.

[jcruise201]

I will get pictures this week and post them.