Rebuilding the Whale Gusher (Henderson) Mk 5 manual pump
By far the most common manual bilge pump, this pump is worth its weight iin gold when you need to evacuate water from your boat and your electrical pump is not working, either because of a failure of the pump or the electrical power supply. Don't ask me how I know.
Sine the parts are made of rubber, they have a limited life. Some suggest that these pumps should be rebuilt every 3 to 5 years. It is relatively simple to do. The parts will cost about half the cost of the pump, or more, depending upon what parts are needed.
A basic rebuilt kit is available from several suppliers under part number AK8050 and includes most of the parts you will need. However, you may need additional parts for your rebuild project. I recommend disassembling your pump and taking a look to determine what parts you will need to replace before you order a rebuild kit. In my case, I needed not only the basic AK8050 kit, but the additional kit containing the diaphragm plate, part number AS0561. The additional kit includes the pivot arm and other parts that I did not need. You may find that the cost of all the parts you will need total an amount that is withing $25 of a new pump.
I ordered the rebuild kit AK8050 before I disassembled my pump and discovered that I needed to replace the diaphragm plates as well. Mine were metal and had been eaten away.