I wouldnt sand blast as it is to much trouble i think..I done my os 46 and 50sx this morning in anti freeze and it worked like a charm..Look brand new and only boild them for about 30mins..Pic only shows how dirty the 50 was but the 46 was in just as bad..And the assembled motors after cleaning..

Pitty the 50 is going back behind it extra's cowl.