I have a Merc 120 GM. Occasionaly when I'm cruising at 3000rpm or higher it will start to smoke a little bit. It seems to be coming from the top of the block around one of the center bolts. It doesn't run hot or knock. It is an older engine, but it was rebuilt recently. I'm just wondering if I should be concerned w/this or if it should be expected with an older engine. I have done a compression check to look for cracks and this has turned out fine. Any Suggestions??
