From looking at available diagrams it seems that there are three phases in the stator, with two usually connected in parallel, sometimes with a hi-lo setup that opens the circuit to the two phases connected in parallel.
Are these three symmetrical phases, 120 degrees apart, or are two actually wound parallel?
Mine seems to have a full-wave selenium rectifier (though the wiring diagram seems to show it as a bridge) and a hi-lo switch. The optional regulator shown appears to be a shunt device but the innards are not detailed.
If it is really a proper three phase stator, the logical wiring would seem to be to use a common 3 phase bridge rectifier block and an FET regulator as discussed in a previous thread.
These same unregulated-alternator problems (overvoltage, etc) prevail on OMC outboards of late 60s-70s vintage.