What year is your H23?
my boat is an 86. i am about to go the same place. my issue is water in the back keelbolt area which is obviously coming up from between the double hulls. i am reasonably sure that my keel/hull joint is sealed. but, i do have some pre existing damage in this bulkhead laserette area, (rot), that i want to take care of. its not terminal looking but if left unattended will become that way. i am very curious about the double hull construction layout. for instance, since i seem to only get water in the back keelbolt area, not the middle or front areas, are there bulkheads under the sole between the inner and outer hulls that possibly seperate these 3 keelbolt areas? if so, and there is water here, that's not good. my laserette itself stays bone dry. have you figured-out the construction details under the sole? in my case, since the bulkhead damage doesn't look too serious i was considering using some "get rot" and then reglassing the joint. then to then keep the area between the hulls dry i was thinking small bilge pump mounted between the hull and sole back near the rear bulkhead. i think a 3 1/2" rule would fit between the hulls and then cover and gasket the hole i cut to install it. i was planning on running the output side of the small pump about where the middle hole in your picture is and from there out the transom....or maybe just "T-ing" into the pre existing hose i already have running from my rule 1500 which is already mounted in the laserette just aft of our bulkhead and plumbed out the transom. (drilling here and finding a pre existing "pipe" would be an interesting situation!). if there are bulkheads under the sole a pump back here would only take care of the back area. have you per chance tried to run a long rod up the holes to see how far they go or what you run into?kudos for your persistance....william