If you have a floor jack, you can get someone outside the boat to gently put some pressure on the keel (while the boat is on the trailer) and from inside you can try to pull on the pivot bolt until you feel the pressure is zero. This takes some trial and error
"... too much bubba, let it out a little... no! no! too far... jack it back up a smidge"
But once you get the pressure off of the pivot bolt, you can pull out the bolt and check if you need to replace the pin, washer and gasket. Might as well since you have already done the hard part.
Making a new gasket is not hard. Get a thick SS washer and make a tape dam like seen in this pic...
View attachment 207678
Fill in the dam with goop and let the goop harden for a few days. Remove the tape and trim your new gasket with some scissors.