From what I can see, this is a daggerboard and I don't see why it can't be completely removed (pulled up and out of the trunk) for transport on the trailer.
One of the basic principles of sailing is not to run aground, so keeping this in mind you shouldn't have any problems once you have fixed the damage that the previous owner did, not adhering to this principle. We have a centerboard and a plaque velcroed next to the GPS that is red and says "board down" and reverses to say "board up" in black, just to keep us on our toes. Perhaps something similar might help you, though I doubt you'd not realize your board was up if you tried to sail, or looked at it.

 

There is probably about 225 to the complete 550 lbs of ballast in that lifting keel so it would probably be quite a chore to completely remove it for trailering.

Most would just have a keel support on the trailer for it to be lowered onto to help stabilize it on the bottom and protect it from snapping the winch and dropping onto the roadway or on top of the axle.

I would not be surprised if through the years the rubber top gasket and shock pads on the bottom fell off and no one did anything about it or even noticed. Yes it is possible as delivered they just relied on the wedge shape at the top to keep the keel from rattling too much when it was lowered all the way and thought the few times it rattled while in shallow draft would be acceptible.

Lifting Keel, Swing Up Centerboard or Stationary Keel they all should be inspected for damage and repaired after a grounding.

Pictures of the gutted interior makes it seem like easy access however I believe that keel trunk and lift mechanism on the Parker Dawson is in the wall of the head and covered with paneling on all sides.

Does it look a bit like this:

 

Most would just have a keel support on the trailer for it to be lowered onto to help stabilize it on the bottom and protect it from snapping the winch and dropping onto the roadway or on top of the axle.

This^^^. You really don't want to trailer a boat with a weighted keel or daggerboard and rely on the winch to keep it up. Raise it with winch, float the boat onto the trailer, then drop it onto the support once the boat is inthe right place on the trailer and secured.

 

Yeah the interior is gutted and everything is visible and easily accessible. There's actually a port light at the top of the cabin that's there for when you need to remove the dagger board. I think it is ballasted, as it does feel pretty heavy trying to move it around by hand. Not 550 lbs though,
at least I don't think. There's a square tubing that's bolted to the "cabin" roof/deck that the board pulley assembly hangs from. The winch is located on a non structural bulkhead just on the other side of the trunk. I'll try to get some more photos tonight.

As for the gasketing and foam, can you explain more where you think that would have been located? There is a wedge at to top of the daggerboardas you described, would it be on that?

Someone in another forum ( http://www.ybw.com/forums/showthread.php?7540-Poacher-trailer-sailer-info-sought ) mentioned retaining clips, and another poster mentioned a piece of stainless steel rod laying around in the boat. I'm not sure what this refers to and Googling for retaining clips just brings up automotive forums. There isn't a hole for a pin or anything in the trunk, so I don't think it could be that.

 

The gasket if they had one would have been around the top of the centerboard trunk to minimize water percolating up over the top of the trunk when driving the boat hard. It could be like a door gasket with a bulb or even flat neoprene.

My boat is a simple open picnic boat with a dagger board that weighs about 50 lbs and lifts with a solid steel suitcase handle. Its gasket is glued inside the upper rim of the trunk. The dagger board has pin holes in the trailing edge to allow it to be pulled up and pinned at one of several shallow draft positions. There is no pin hole in the trunk but there are 2 stainless steel plates on top of the trunk for the pin to rest on so if you do go aground the dagger board is not locked 100% and can slide up a bit and skid along the bottom instead. On mine I intend to put on a safety lanyard to prevent the dagger board from getting lost in a knockdown.

 

Unfortunately, the boat has been out of the water for at least two years now, but still has sopping wet wood in this location. I poked around a bit and tried to see how deep I can poke through the soft wood and the damage felt limited to just one side. I guess I'll have to sand the bottom paint off first to see how bad of a shape the gelcoat and laminate are in this area.

I read the West Systems fiberglass repair manual and was going to proceed with the pegboard hole drying method. Maybe hook up a vacuum pump to make it go faster. Then, as the manual says, I'd fill the holes with epoxy and try to fill and gaps that delamination may have caused. Do you guys think this will be good enough or will I have to cut larger patches to see if core replacement is necessary? I'm afraid that if it's still this wet, there may be a lot of rot in there. Is there a way that I could reinforce this area better as well so that this damage doesn't happen again? .

If the boat has been out of the water for two years and the area is still wet something is very wrong there, unless the area has been getting wet from the outside or leaking in the cabin. If the core is that soaked still, a shortcut like west system explains might just hide the water soaked area deep under a shoddy repair. The best way to repair it is to grind away the bad laminate and remove and replace the rotten wood. Or remove the wood and build it back up with solid fiberglass and resin.

You can reinforce it all you want, the best way to make sure it does not get damaged is to not run aground. Once is one to many. If you want to use your keel as a depth sounder trade your boat in for a swing keel one. There is some knowledgable boat owners here to talk you through the repair but you might want to check out the Trailer Sailor website for more specific small trailerable boat suggestions.

Here is a site showing a keel trunk repair project, from Judy B.

Album Index for album 0021: P19 Keeltrunk Project

Good luck with your repair.

 

Here is an album with more images:


As you can see the dagger board is also a little damaged at the top on the trailing edge. The trunk itself feels pretty solid, so I don't think I'd need to beefen it up any. The only damage to the trunk is at the bottom where the wedge of the dagger board mates with the wedge of the trunk at the hull.

I did notice something today that can be seen in one of the photos. There is round hole in the metal fitting at the top of the dagger board, and this hole extends down 2 to 3 feet inside the dagger board. I'd say it's 2-1/2" in diameter. Could this be the for retaining clip or stainless rod that was mentioned on the other forum? I could see a rod or post doing up and clamping to the top of the trunk?

I also got in contact with someone in the UK who owns one of these boats. Hopefully I can get some information from him too.