new bottom job - polyester or epoxy?

Yeah, I might try this again one layer at a time. I may have rushed things in trying to beat the cure. It's possible I used too much hardener in the first layer. Can't really comment on the age of the resin product (West Marine). I don't recall seeing any expiration date on the can.

Using too much MEKP means your resin is going to kick off super fast.
Using expired resin means the resin may not fully cure.

Neither of these were your problem. Poor adhesion is most likely the result of poor surface prep or contamination.

sm

Well, I tried this again paying especially close attention to surface prep, mixture and even waited for ideal temperature and humidity. I let the first layer fully cure and sanded before adding a second layer. The results were marginally better but I would still not call it a proper bond. I really cannot fault the product or process this time. I'm of the opinion that perhaps my 30 year old gel coat (all 30 years in the weather) is simply too parched and porous to ever achieve a great bond with the harder (than epoxy) polyester resin. Just like me, my boat is aging not so gracefully.

First question, why are you fiberglassing over the gelcoat? If the hulls aren't worn through the gelcoat, then there's no need to add glass. Just fair the hull and then gelcoat.

For surface prep, you need to roughen the hull well using 80 grit sand paper. Sand the surface in multiple directions, at 45 degrees to one another. Then clean with acetone. I did a bottom job on my 27 year old Hobie last year and it's held up fine. The age of the boat shouldn' be an issue.

sm

The keels are worn to the point of showing pinholes and taking water. There is no gel coat left on the keels. I've wrapped them with 4 in, 8 oz glass tape. There is no way to avoid some gel coated areas unless I take the hulls all the way down to the fiberglass with a belt sander or something more aggressive than I want to chance. I've done bottom jobs on two other boats using epoxy and got a pretty good bond. Polyester just isn't getting it. It is adhering more like a coating rather than a true bonding.