I know that with the straight 1350s (not 1350/1550) Mercury wants them back every 100 hours to rebuild them at a cost of $80k+. My buddy has a Skater 40 with a set and pulled them out and sent them back to Merc at just over the recommended 100 hours. He said he spent just under $180k and he pulled the motors and put them back in himself! They're absolutely incredible motors (1,400+ HP at the crank on 91 octane unleaded), but all that performance does not come cheap.