strange one

Amongst the pile of repairs I've got is a speed boat, guy crashed it and partially sunk it. I've changed the smashed prop and 're attached the shaft to the motor and replaced the water logged rx but when I plug in the battery the motor bursts into life! it's a water cooled and sealed esc. can these things fail "on"?

Was his or your Tx different and was one a Futaba?
Their throttles work in opposition to everyone else.

All sorted chaps, the Speedo had failed "on" probably due to the whack the prop shaft and motor had, always assumed they failed safe?
Simon, I didn't just fit a new rx, it was a obscure make so it's had a new one with matching tx.