I have a 1989 Johnson 175 outboard that I have removed the heads to replace the head gaskets.<br /><br />I found a piece of the cylinder block missing from the outside of the sleeve on one cylinder. The part is approx 1/8 inch of the aluminum casting near the top of the cylinder and looks like a crack that may get bigger. <br /><br />The sleeve seems to be fine and the motor runs great. <br /><br />My questions are:<br /><br />Is this a death sentence for my motor?<br /><br />Can the motor possibly continue to run this way?<br /><br />Will this cause overheating since the cylinder sleeve is in direct contact with the cooling water?<br /><br />Thanks in advance<br /><br />Chris