buying a atomic-4 please help

[rbtmoon]

I want to buy a boat that has an atomic-4. the engine runs great, no smoke,plugs are clean, exhaust pipe clean, starts well, runs smooth. looks clean and well cared for. Just to be safe I did a compression test on a warm engine. The results surprised me. #1. 110 #2. 100 #3. 90 #4. 120. Accourding to all I have read the range 90 to 125 is acceptable but shouldn't the compression be only 5 or 10 pounds difference on each cylinder????? Can anyone help me out? I really want this boat but I cannot afford to have major engine problems. Is there a valve about to go on #3? Please help!
Thanks

Robert Moon