'84 Evinrude 150 Compression with Crossflow Heads

How do you check the compression on the Evinrude 150 with the crossflow heads. I heard there was something different needed to be done, like remove all the spark plugs.

 

Just like you would any other motor. Pull the plugs out, its best to ground the plug wires or use a jumper to spin the starter without the ignition turned on. Screw in the tester and spin the motor until it stops increasing. You can leave the throttle open or closed, just do it the same each time.

Removing all the plugs allows any motor to spin faster, the faster it spins the quicker it builds compression, plus its normally a little higher the faster it spins.