hi phil  i replaced all my hatches with lewmars.   the head hatch is a #10. it was a nearly perfect drop in replacement.  they make two profiles.  one is lower than the other.  i put the ocean model on my boat which offers more water intrustion protection.

Hi, James.  How hard was it to replace this hatch?  I've never had to do this but I probably will have to someday, so there is a bit of "fear of the unknown" surrounding it :-)

hi ben,  after removing the screws i used a cordless oscillating tool to cut through the 4200 on the inside of the boat. once you get the inside flange free of the boat it comes out pretty easy. you will want to have at least two blades available because they get really gummed up from the sealant. then move to the out side of the boat to free the exterior flange. i first put a couple layers of 2'' wide blue tape down on the deck around the out side of the flange to protect the gelcoat. then hammer a really stiff blade putty knife under the flange and lift gently trying not to bend the blade. repeat around flange over lapping the width of the blade to cut through the sealant. once you are able to get a little space between the deck and the flange start putting wood shims under the flange to keep it from getting sucked back down by the tenacious 4200. repeat until it breaks free.

hello again ben,  FYI  i highly recommend butyl tape to reinstall the hatch.

Thanks for the info, everyone.  I love this forum!

I had the owner of the boatyard a few years ago tell me they would heat up the area with a heat gun or heat lamps when trying to remove items that were sealed with 4200 or 5200. I used a heat gun for a thru hole fitting and was surprised how easily it came apart.
I also saw a "How to" removal of a hatch where they used 2X4's and threaded rod to make a puller to slowly extract the frame with even pressure. Most descriptions I have seen also slice the sealant as best they can as well.

On the newer boats Catalina used butyl.  Mine were clearly redone with silicone.  Used some plastic wedges I got at ACE to slowly put pressure.  Not a single curse word was uttered. 

I rebedded with mainesail's butyl and they leaked when tested.  You could see light.  Pulled and rebedded with white butyl from the Catalina factory and worked perfectly.  This tape was much softer and made a much better seal.  Had the same problem on the mast collar.  It actually cocked the collar.  Swapped it out for the white Catalina butyl and problem solved.

my suspicion is that different butyl works better in different places.  Mainesail's butyl is awesome for deck hardware.  It strength and tenacity is perfect.  I think the hatches and collar work better with softer butyl that can be put on thicker to ensure a good seal.

this is an easy job that just takes a little patience.

if you are looking for new hatches, I saw some #10 hatches at the Catalina store last week.