Things You'll Need
Sewage discharge hose
When you find you must troubleshoot the electric marine toilet aboard your boat, your efforts are focused on three areas -- the water supply, the pump and the macerator, which is the grinder that reduces sewage to small bits before moving it the the marine sanitation device, the seagoing equivalent of a septic tank. Because marine toilets are modular units, the solutions for the problems disclosed by your troubleshooting efforts are often solved by removing a few bolts and replacing parts.
Move your boat to the sewage disposal station. Connect the sewage discharge hose to the deck discharge port of the boat's marine sanitation device. Unlock the padlock on the sewage discharge valve and open the valve. Turn the sewage discharge pump on and pump out the marine sanitation device.
Flush the toilet by pressing the flush button. If there is no water flow, ensure the boat's water tank has sufficient water to supply the toilet, by visual inspection of the water tank's level. If the water supply is sufficient and the flow of water is non-existent or sluggish, you should suspect a problem with the pump.
Push the flush button again and place a hand on the cover of the pump. Feel for the pump motor's vibration to ensure the pump is operating. If the pump does not function when you push the flush button, remove the pump mounting bolts, using an adjustable wrench. Place a new pump motor on the pump head and replace the pump mounting bolts.
Inspect the floor under the pump. If clear water is standing under the pump, a damaged seal and, almost certainly, a damaged impeller in the pump are the likely causes of the reduced water pressure in the pump.
Remove the bolts that hold the pump motor, using an adjustable wrench. Apply gasket sealer to a new pump seal. Replace the impeller and the seal around the impeller. Return the pump to its position and reinstall the pump motor mounting bolts, tightening them snugly.
Go to the marine sanitation device -- the holding tank for the toilet, located below-deck -- and loosen the hose clamp that connects the sewage hose to the marine sanitation device, using a screwdriver. Place a 5-gallon bucket beneath the sewage line.
Return to the toilet, crumple a few sheets of toilet paper, place them in the toilet and flush the toilet. Return to the 5-gallon bucket and inspect the toilet paper; it should be ground into small bits, no larger than 1 square inch. If not, loosen the bolts that hold the toilet unit to the macerator that grinds the waste, using an adjustable wrench.
Remove the toilet. Loosen the bolts that hold the macerator to the floor. Remove the macerator and the old wax seal. Place a new wax seal over the pipe-stub that leads to the sewage hose. Place a new macerator's discharge outlet over the wax seal. Replace the toilet on top of the new macerator. Tighten the bolts that connect the toilet to the macerator.
Go below once more, to the marine sanitation device. Reconnect the sewage hose to the marine sanitation device.