Reply To: Evinrude 7.5 idle

[David Stanton]

To add to what Fleetwin said in the post above, if your compression gauge has a hose, and if the gauge relief valve is at the gauge end of the hose, the volume of the hose will add to the volume of the cylinder and give a low reading on small cylinder motors. I have one of those gauges that reads 40 pounds compression on a JW 3 HP Johnson, and if I remove the hose and hold the gauge with out hose but with a pointed rubber end in the spark plug hole, compression reading nearly doubles. The bigger the cylinder, the less the error becomes.
Dave