Be sure to do several checks of the lower unit oil after running until you are satisfied that there are no water leaks in the lower unit seals.  With the motor on the trailer slowly rotate the propellor and watch the prop shaft for any wobble this will indicate if there is a possible bent shaft..If water is present in lower unit, possibly worn seals or signs of a more serious problem..After checking routinely and getting the same results you will know how good a shape your motor is in...
 
Tommy