These are the modular replacement motor cartridges for Johnson's "Cartridge Pumps". You can recognize cartridge pumps by the large "wing nut" on the top.
With Johnson's Cartridge series of pumps, bilge and livewell pump cleaning and maintenance no longer call for complete disassembly of the pump and its mount. You can now leave the pump casing attached to both the boat and the hoses. The cartridge bilge pumps can be removed for routine cleaning or complete replacement without the use of a single tool.
Simply lift a tab at the top of the pump, give the cartridge a twist using the Wing nut tabs, and pull it out. That’s all there is to it.
The cartridge contains an all-in-one motor/impeller unit with no loose parts.
Slide the new motor cartridge into the housing and twist it home.
Cartridges are available with nominal 500, 750, 1000, and 1250 gallon per hour outputs.
The three lower output cartridges are all the same physical size, and all discharge through a 3/4" hose — so if you wish, you can upgrade a lower capacity pump to a higher capacity simply by switching to a higher output cartridge.
The 1250 gph output cartidge, however, can only be used in the 1250 gph housing, as it discharges through a 1-1/8" hose.