I agree with the gauge being the trouble. There is a check valve somewhere in the gauge, usually at the cylinder end of the hose or fitting- depending on what kind of gauge you have. If the check valve is sticking, you will have low compression readings. Your pressures are pretty low for a wet check.
Have you used that compression gauge on other engines, and found better/higher pressures? If not, the check valve in your gauge may have been replaced with a tire valve, which will/may cause lower compression readings because tire valves have stiffer springs. A stiff spring means delayed opening under pressure and early closing as the pressure nears the peak- result- a lower pressure reading. Most compression gauges have very weak check valve springs.
Harvester
