It's the primer, most likely, that's the issue.  I used PreKote on the outside of my skerry and regretted it.  It made the Brightsides softer and easier to damage.  The Brightsides on the interior was laid down over just the sanded epoxy and it seems a lot harder. I get a lot of sand in the bottom and while I have the SeaDek matting in there, the sand still gets on everything else and doesn't do excessive damage to the pain.  Also, I'm not easy with the oars, tiller, other stuff banging around and aside from a few chips on edges, it's pretty solid.

Where I've repaired my outside paint and sanded down to the epoxy before repainting, it is harder to damage than the original areas which were painted over primer. I didn't thin the paint at all.  In any case, Brightsides is not armor, it will scratch, that's just life.  My skeg tends to stay pretty scuffed up also but it's just the sacrificial outer layer of wood.  On the Skerry, the kit has a small cap strip that goes over the main plywood skeg w/ screws.  The instructions were to epoxy the bottom w/o it and put it on afterward.  That way, if badly worn, it's easier to remove and replace.

On the bunks, I went with carpeted bunks, which I think will be kinder to the finish than plastic ones, in terms of abrasion resistance.  Plastic/PVC tend to create "stiction" in my experience.  I do make a point after launching in salt water of lifting the boat up and thoroughly rinsing the bunks along w/ the rest of the trailer when I get home, to avoid the build up of salt crystals and scum that could attract road dirt.

   I know some people put a brass or stainless steel half round on the skeg if they are in rocky waters to protect the wood.  CLC even sells them, for a pretty reasonable price.

I agree that it sounds like your paint is much softer than normal.  I used Brightsides on two kayaks and the paint has held up well.  I used PreKote primer and would probably not do so again.  It likes to absorb water in a humid climate (I live in FL) and creates vast plumes of dust when sanding.  I note that you used "oil based primer" but did not mention a specific brand.  Did you use something other than the two listed by Interlux?  If so, there may have been a chemical incompatability that prevented the paint from fully hardening.

On a last note, if you want something a bit tougher than Brightsides, take a look at an airboat coating called Wetlander.  It is expensive but easy to apply and VERY tough.  

Mummichog - I also painted the interior of the boat with Brightside directly on the epoxy with no primer and the finish seems much more durable than the exterior Brightside with primer. Interesting that you had a similar experience.

Mark - I used an exterior oil primer, maybe Sherman Williams or something like that. Not an Interlux product. Live and learn, I suppose. Perhaps a fall project will include stripping down to epoxy and repainting.

Thanks for the replies!

" Live and learn, I suppose."

Part of life. And boat-building.

Easy to forget these products are designed and manufactured as systems. I don't know anyone who'd pick an epoxy resin from one manufacturer and a hardener from another. It's obvious (to most?) the resin and hardener should be from the same company and intended for use as a system.

Paints and undercoats / primers need pretty much the same mindset.

My only experience so far with Brightsides was in an interior compartment, applied over a  hardware store Rustoleum oil-based primer. Far as I know it worked just fine, seems hard enough after eight months but hasn't seen any in-use tests yet as my project build hasn't been launched.

For the exterior I went with Kirby's Marine Enamels over their brand of primer. Again everything seems to have worked as intended but only time and use will prove it.

My guess as to what went awry with your finish is some chemical incompatibility as others have also suggested.

And you may very well find that after taking your hull back to the epoxy that the best result may come from your choice of finish paint applied w/o primer first.

Getting closer to launch day with every little job I complete...

   I used Brightsides on my Jimmy Smith 2.  No primer and no paint thinner. I just painted it on the scuffed epoxy.  Has lasted well on hull exterior and the seats. I store the boat on wood racks. Transport it on carpeted boat trailer bunks or on the forklift. 

spclark, Nora Jane is looking sharp!

I sprayed silicone on the bunks yesterday and that made a positive difference, she slid off the trailer with little provocation and and I didn't see any new paint scuffs. 

It was my intention to "sail the paint" off this boat anyways, so I just have a bit of a head start!!! 

-Mike

Thanks for your comment Mike! I'm very pleased with how this build is turning out (after some 20 months! And I'm not quite done yet!) for a "first-time" kit project.

Silicone can do wonders, I agree! Did your trailer come with PVC bunks? That's unusual in my experience; the flat, smooth surface may seem slippery but can generate quite a bit of momentary heat when an object - your painted hull in this case - is slid along it. For my trailer I opted for fairly long, treated-wood bunks then covered them with carpet made just for the purpose. Hopefully it won't damage my paint job.

When it's time to repain your Pasagemaker, remember to do a bang-up job of getting any remaining silicone off before you start the repainting!!