Mike there is no easy way, One way is to heat the mid section to expand the metal and loosen the crap that is built up around the studs, it can also get stuck on the top of the prop shaft, so I recommand removing the lower unit that will eliminate that possiblity. If the lower comes off then you know its the bolts, also buy yourself some putty knifes and begin trying to drive then in between the adapter plate and power head. be careful not to damage the surface area ,lots of heat and shaking, put upward pressure on the powerhead and rock till your arms hurt, good luck!!!!!!
If you use heat you need a torch of some sort, a propane tank won't get it hot enough, please be careful with heat cause you can do damage if your not careful!!!!!!!!
When you do get it off , make sure your friend uses some kind of anti seize lub on the threads and grease the top of the prop shaft, again good luck!