Water Pump Impellers
If the seawater cooling pump stops pumping the usual cause other than a blocked intake is impeller failure. To repair after closing the thru hull, simply remove the cover or pump case depending on model and change the impeller. To remove the housing on Sherwood pump shown remove the 3 bolts shown. A 10mm or 7/16" box end wrench is needed. Upon dissassembly it is important to remove any broken impeller blades from the pump housing and output hose. The larger pieces generally get lodged in the 90 degree output fitting. The fittings screw into the pump in place of the blue plugs. Disconnect the hose and shake to remove pieces. Needle nose pliers or forcips work well and getting pieces out of the fitting.
After the new impellor is in place it is important to lubricate it to prevent wear until water is circulating. Vegetable oil or other non petroluem based lubricant should be used.
An alternative to the black rubber impeller is the one manufactured by Globe. It is made from a blue colored elastomer (plastic) and has a 15 minute run dry guarentee. They are available from Defender. This is the information for the Sherwood G908 pump (impeller Part# 9000): Impeller Item #: 301959, Manufacturer: GLOBE, Defender Model #: 610/01-12-1440, Shipping Weight: 0.10 Lbs, Price: $55.99 If you have the 10077 (Oberdorfer I think)impeller the corresponding Globe part# is 1130.