MY BOAT IS A 1977 EVINRUDE 75 HP. I DONT EVEN KNOW IF THE IMPELLER HAS EVER BEEN CHANGED. I BOUGHT IT FROM MY UNCLE AND I KNOW HE HAS TAKEN GOOD CARE OF IT. IT RUNS GOOD BUT I KNOW I NEED TO CHANGE THE IMPELLER BECAUSE IT WAS NOT RUNNING TWO STREAMS OUT OF THE THE TOP. S0 I TOOK THE 4 SCREWS OUT...