If I am not mistaken you bought a Watkins 27' sailboat.
WATKINS 27 Sailboat details on sailboatdata.com
The spec sheet on this boat shows that it is a shoal draft boat rather then center board model. Still I would not be surprised if your W27' is a C/B model as builders often vary a few hulls from the general spec.
I would assume that marine growth/barnacles is the reason the C/B is stuck. I'd suggest that the best way to get that growth out of the C/B trunk is mechanically. A long, thin, flat piece of metal would make a good tool for working around the trunk to remove the buggers. Using Scuba gear would make this job much easier or you could hire a diver to help with this.
I have heard of others pouring bleach into the trunk which would likely kill much of the growth but not necessarily remove their shells. It also does not sound so good for the local water quality.