I have an MD6A also with a dynastarter and generator combo unit.
It does get quite hot also. I bought the boat last season so I don't know if this is normal.
But.. I have my belts to the dynastarter very loose because if it is, infact the bearings that are getting old, the lighter load on them will prolong it's life.
I plan to get the thing opened at some point and have the bearings changed out.
ps. generator is not connected.
pps. also, i just remembered. I did talk to a starter guy that says if the thing is conected to the circuit wrong, it may be producing heat electrically by working against itself.... developing..