Home › Forum › Ask A Member › Mercury KF-7 lightning – bottom cylinder drops out. › Reply To: Mercury KF-7 lightning – bottom cylinder drops out.
Well, there’s the hole in the old seal….That’s the crank case drain. My thought is maybe you got a new seal that wasn’t really designed to tolerate gasoline and it failed prematurely? There is a way to test newer Mercurys for crank case pressure but it relies on already-installed, small nipples, that you attach to a small check valve and a pressure gauge. The check valve cancels the negative pressure pulse and allows the gauge to just read the positive pressure. Obviously, KG7s have no such nipples.
I usually coat my gaskets with oil before I install them. That way, I have a chance of taking them apart and maybe be able to reuse them one time. Too bad you couldn’t just loosen the cylinder block from the crank case and pull the lower bearing carrier off and have a look at the seal.
Long live American manufacturing!