. >> miami-dade police sargeant james barrett says it's very difficult to trace the stolen engines, in part because serial numbers get erased or altered. >> we have to start from the manufacturer and work our way back to see where that motor is supposed to be right now through the records. >> all these yamaha engines sitting in plain sight even experienced investigators can't tell if they've been stolen we're there when a team of miami-dade police officers shows up unannounced to a boat repair shop it didn't take long for them to find what they suspect is a stolen boat and two stolen engines. one of them, a yamaha. >> this engine here doesn't have any number it has a sticker where it used to be but the number seems to be obliterated or for some reason it's not there so without that, without that, this particular engine, i can't identify who the owner of the engine is. >> police remove the boat and two engines for further investigation. the owner of the yamaha engine shows up he tells us he paid $3500 for the used engine from a local repair shop. >> what i worry about is losing the mone