EE WAS ASSISTING WITH REPLACING A 13 HP FLYGHT PUMP. HE WAS MANHANDLING THE PUMP TO GET IT INTO DEEPER WATER. HE SAID HE FELT SOMETHING FUNNY IN HIS BACK. WHEN HE RETURNED TO WORK HE SAID HE WAS HAVING BACK PROBLEMS. HE ATTEMPTED TO WORK SHIFT BUT LEFT AFTER 1 1/2 HOURS.