Hi,
I just got a 1978 150 HP Merc I6 this winter (along with a 1978 Checkmate Try-Mate 1).
Compression was around 136 +/- no more than 10 psi.
I have replaced all fuel lines and fittings, rebuilt carbs and fuel pumps (2) (they were all bad), primer bulb, then the basic stuff like impeller...