I know on my old Caracal it was mounted at the rear of the sump, thru the hull, and did not have a replaceable motor. I would first check for voltage at the pump before removing it. For the voltage check, you should have brown and black wires going to the pump, dis-connect them and see if you are getting 12 volts when turned on, if not then it may be your switch or timer. If you do need to replace the pump I would get one with a replaceable motor and use some 3M 5200 marine sealant when installing the new thru-hull fitting. This is all assuming that your pumps are original and have not been replaced at some point. Any pics you could post of the sump could help a lot.