You can remove the cover of the bilge pump, while it is still attached to the bulkhead. It faces to the port side and is held in place with Phillips headed screws. There are two rubber flapper valves inside, that are held in place with two each of tiny Phillips headed screws. First cycle the pump (the float switch is within easy reach and you operate it manually) to make sure that the motor is working and the diaphragm reciprocates. You then cycle the pump so that the diaphragm is away from the valves to give you more clearance. You can unscrew the tiny screws and either invert the rubber flapper valves or replace them. I have used a quarter inch socket to hold a Phillips screwdriver bit and then used this to loosen the two Phillips screws. After they start moving you can probably fit a jeweler's screwdriver in to unscrew them the rest of the way. Don't drop any pieces in the bilge!!! Also check that the valve in the strum box is working. There is a replacement valve in the rebuild kit and they are easy to replace. You just pull the hose up out of the bilge and take the snap-off cover off the strum box to access it. I have done all of these operations while at sea but I can guarantee the flapper valve replacement is easier at the dock.