is this part replaceable ? when I got the boat I found it in two pieces in stuck in the prop...I've changed the waterpump in the lowerunit and the prop and it runs great...no overheating at all...figured out what it was the other day while glancing thru the manual. from the pictures I'm guessing it's in the pipe between the 2 rubber bellows off the manifold...from the manual I can't tell if it's a seperate part of if it's part of the pipe itself.<br /> Do I really need this ?