Compression Question Late 80's Evinrude 40hp

[Baitcaster]

Hello I have late 80's Evinrude 40hp and I did A compression test on it and the top was A solid 140 and held and when I checked the bottom it flew up to 140 the released down very fast? I just wanted to get some info if any takers ever heard of this? Before I go getting it taken apart,I was thinking A leaky head? Possilbly. Let me know,

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