The homometallic ludwigite Fe3O2BO3 has a complex structure made up of corner- and edge-sharing FeO6 octahedra and exhibits a number of apparently puzzling magnetic properties. The reasons for these properties were probed by examining the trends in the spin exchange interactions of Fe3O2BO3. To analyze the relative strengths of spin exchange interactions in such a complex magnetic solid, we first generalized the method of spin dimer analysis and then employed the resulting formulation to investigate how the magnetic properties of Fe3O2BO3 are related to its reported crystal structures. The spin-orbital interaction energies calculated for various spin dinners of Fe3O2BO3 provide estimates for the relative strengths of the associated spin exchange interactions, which in turn account for the observed magnetic properties of Fe3O2BO3.