Mercury Optimax Diagnostic Guide., Page 15Get this manual
OPTIMAX DIAGNOSTIC GUIDE
Procedure 12
RELIEFPOPPET VALVE
The reliefpoppet valve is used to control water pressure at high RPMIf the engine temperature is below normal after the thermostat kit is installed (Procedure 11), check the reliefpoppet valve for: Leaking through or around the valve diaphragmclean the cover surfaces and replace the diaphragmRubber grommet is out of place or missing on the carrierreinstall or replace the grommetCarrier (which is pressed into the adapter plate) is loose or installed at an angleremove the carrier, check for debris between the carrier and the adapter plate, install the carrier and stake it into placeExternal leak past the cover gasketreplace the gasketDark sooty appearance on the spring and valve, which is an indication of an exhaust leak from the powerhead base gasketreplace the powerhead base gasket