Yamaha Marine Outboards F4A/F4 Factory Service Manual, Page 88Get this manual
INSP ADJ
GENERAL
Compression pressure: Standard: (without decompressor operation) 660 kPa (6.6 Kgcm293.87 psi)
If it is below the specified pressure Squirt few drops of oil into the affected cylinder and measure againFollow the table belowCompression pressure (With oil applied into cylinder) Reading Higher than without oil Same as without oil 7Install: