1990 Johnson Evinrude "ES" 40 thru 55, P/N 507872, Page 293Get this manual
IMPACT RELIEF 1When the engine hits an underwater obstruction, extreme pressure develops above the piston
2The extreme pressure must be vented and the cylinder rod must extend to allow the engine' lower unit to clear the obstruction 3Under extreme pressure, five IMPACT relief valves and one UP relief valve fluid to pass through the piston as the cylinder rod extends
will open to allow