We have a Nordhavn 47. It comes standard with a regular diaphragm bilge pump mounted outside the bilge, a high water emergency 3700 gph bilge pump and a gallon a stroke Edson manual pump. We upgraded our manual bilge pump from Aluminum to bronze. We also added a "crash" pump. It is the spare emergency pump is pre-wire with a circuit breaker and alligator clips set to be connected to the alternator pre plumbed and stored in the engine room. We use the manual bilge pump for two reasons. 1) The main bilge pump has failed twice. You only know the pump has failed when the water level begins to rise. Of course the bilge pump has only failed while we have been on multiple day legs at sea. The first thing I like to do is lower the water level before I start working on the pump. While it has never failed in seas too rough to work on it, having the ability to delay working on it is nice. 2) I use the manual pump to at the end of a trip to empty the bilge out. The normal bilge pump does not get the last 1/2" of water, and I like to have it dry so I can clean / inspect the bilge. ---------------------------------------------- We have the manual bilge pump for two emergency reasons. 1) Our boat is design to operate after a lightening strike takes out ALL electrical systems, we needed a manual pump to handle keeping the bilge dry. 2) Also if we need additional pumping capacity after we arfe taking on water. The problem with taking on water is it common to have the water wash junk into the bilge and existing pumps get plugged. This provides the ability for a third pump to be working. This pump provides the redundency for a plugged pump. ------------------------------------------------ We are very happy to have a manual pump! Ours is mounted in next to the hatch used to access the engine will someone is sleeping in the master stateroom. It is pretty comfortable to use, you sit to operate it. Make sure you install it where you can operate it comfortably (for many many minutes) near an exit in case of fear of sinking, make it large enough to pass LARGE solids, at least 1/2" and if you plan to use it often like we do make sure it is bronze. (According to the Edson the aluminum one needs to be flushed with fresh water after each sea water exposure). ----------------------------------------------------