Igneous Rock is formed when a magma cools underground and crystallizes or when it erupts unto the surface of the ground, cools and crystallizes. Magma that erupts onto the surface is called lava. When magma cools slowly underground the crystals are large enough to see.
Readings for compression tests usually vary between 175 to 250 PSI (Pounds per Square Inch). A higher reading generally indicates better engine performance; however you should check your vehicle manual to find out what the ideal reading should be for your vehicle.
Testing Compression using the leakdown or bounce method. To perform a compression test without a compression gauge, turn the outboard over by hand (utilizing its recoil start at normal starting pull speed), and gauge the amount of bounce you feel as each piston passes top dead center (TDC) position of its stroke.esting Compression using the leakdown or bounce method. To perform a compression test without a compression gauge, turn the outboard over by hand (utilizing its recoil start at normal starting pull speed), and gauge the amount of bounce you feel as each piston passes top dead center (TDC) position of its stroke.