Does AC Plywood need to be primed before skim coated

Long story short, I have a small 2x4 AC plywood that was skim coated, primed and then painted...

It's been around 8 years and now it's started to just crack and the paint/skimcoat JC is peeling right off the AC plywood.

I plan to just scrape it down to bare wood and refinish again...
Does plywood in general need to be primered before skim coated.

I am planning to use Zinnsers primer before skim coating this time around

 

Wood should be primed before any final finish is put on. However, wood is not a good medium for the application of sheetrock joint compound. Could it be replaced with sheetrock and then properly coated? It would not likely crack again as the wood will.

 

It's not a great idea to skim coat plywood because it's apt to peel although 8 yrs sounds pretty good. What's the application of this plywood?

Which Zinnser's primer do you intend to use?

 

Actually in my research, I think I will try wood filler.....and then primer/paint ontop. I will call Zinnsers today as I did not see it on their website but I thought they had a elastomeric type of primer as well.

The plywood is much smaller than I stated. Probably closer to 30" x 13" Deep. I can't really install 1/4" drywall or the like on top. The *front* of it is finished tile. It's the side framing for a basement windows. The 3 sides (sides and bottom) is finished in tile. The top of this is the problmatic AC plywood. The basement does not see much moisture. It's more a ~mud room~ than a bathroom where showers are taken.

I'm thinking 2 coats of wood filler and then sand it smooth...

 

While I've used several different brands of elastromeric paint, I don't ever recall having heard of an elastromeric primer.

Why do you feel you need 2 coats of filler on the wood? I'd apply just enough to get it smooth while sanding the majority of it off.

 

Yes, If you must skim, the less you put on the better. If you get it down to bare wood again and since it is so small consider Bondo or something like it.

Also about 30 years ago I filled some wood with Durabond, (the real thing) mixed with Elmer's glue and no water. It spread really tough but it held for years and may still be holding. It was as hard as a rock and stayed bonded to the wood it was put on. It even held and may still be holding a screw.

Plasterers are notorious for tinkering with different mixes for different purposes.
This one succeeded.