CC V8 pressure relief valves (low speed overheating)

The Pressure Relief Valve is a device that is normally “out of sight, and out of mind” on a Chris Craft. This is the Pressure Relief Valve (see photo link),

http://img.photobucket.com/albums/v472/Dogsharks/Sea Skiff/DSC00965.jpg

and it is used on just about all Chris Craft V8 motors from the late 1950’s onward. The Sherwood Brass sea water pumps have a great pumping capability and at top speeds they are able to over-pressurize the motor. In order to vent off excess pressure, Chris Craft devised a simple automatic method of bleeding excess pressure directly into the discharge riser. These valves faithfully provide service for many years, but they have one flaw, and that is the fact that over time, they are able to be compromised with crud and small pieces of debris passing harmlessly through the system. In the event a pressure valve gets stuck in the open position, for instance, incoming cooling sea water can be short circuited directly into the exhaust system and only a portion of the needed low speed water stream will reach your motor block. This can contribute to low speed overheating.

http://www.network54.com/Forum/424840/message/1164411296

If you have a motor that is getting hot at low speeds, it could be because your PRV is being held open, or your water impeller is worn or coming apart, or the cam inside your water pump is very worn, or there may be debris from a destroyed water pump or other source, somewhere in a critical location in your water delivery system (the transmission oil cooler on some models is a likely location for collecting debris).

Hope this helps someone in the Chris Craft contingent !

Regards, Dogsharks