Leaks in 44' Marine Trader keel

When we re-launched our 1978 MT, it started taking on water, we discovered several cracks (mostly on the port side) where it had been blocked. The keel is a hollow fiberglass tube and the cracks are at the join between the keel and hull. Any advice would be appreciated or does anybody have blueprints or know how these were constructed?

Don’t know if this is appropriate to your situation, but I worked on a boat with a similar situation some years back where the owner decided to fill the hollow keel with concrete and several stout fiberglass rebars.
Of course the cracks had to be patched as well.

Who did the haul and blocking? I would get a good fiberglass guy to do an estimate and present it to the yard that did the blocking.

A yard or anybody would assume that a boat that has a keel is meant to be blocked up under its keel and steadied by jacks along the hull sides.
As long as the blocks are placed evenly, and the jacks just snug, no damage should happen.
I have seen fiberglass boats with incredibly flimsy hulls, where placement of blocking/jacks was very tricky, hope yours isn’t one of those!
Do you have any pictures of the boat on it’s blocking?
Surely you did bottom paint while it was on the hard, was damage not noted then?
That might point to damage during or even after the launch.

I would say unusual.

Something pretty drastic has to happen to crack there is it is often the thickest part of the whole hull.