How To Rebuild Macerator Pump

A quick look at what’s involved in rebuilding a macerator pump.

December 8, 2015
How To Rebuild Macerator Pump
How To Rebuild Macerator Pump Tim Barker

Whether used for the head or for fish-box duty, macerator pumps abound aboard boats. When they fail, these pumps can be rebuilt for way less than the cost of replacement. And with a rebuild kit on hand, if a pump breaks during a cruise, you won’t have to opt for the bucket brigade. Here’s a quick look at what’s involved in rebuilding a macerator using renderings of a Jabsco pump to illustrate. Read your specific service kit’s instructions before actually undertaking this repair.

Safety First
Wear gloves, a mask and eye ­protection. Pumps serving in a fish box, livewell pumpout and, ­obviously, head installations can contain biological contaminants.

Don’t Sink
Close any seacocks connected to the plumbing of the pump. (Remember to reopen after the repair because some pumps might burn out when run dry.)


You’ll need to demount the pump and remove it to a location where it can be worked on. Skip to the “Shaft Lock” step if your pump is not a macerator.

Remove the macerator housing from the pump body (also called the impeller body). This is secured with fine-thread machine screws or studs. There will also be a wear plate and one or more gaskets or washers under each nut or screw head, and possibly a gasket or O-ring between the pump body and the motor body.

Shaft Lock
The cutter blade is secured to the drive shaft by a nut. The end of the motor opposite the pump body should have a screw or bolt covered by a cap or sleeve. Secure that nut or screw to prevent the shaft from turning, and remove the cutter nut, cutter and any gaskets between the pump and motor.


Old Impeller Body
The impeller body or pump body abuts the electric motor and contains the impeller, another wear plate, a shaft seal and the fasteners that secure it all together. Slide the impeller body off as a unit and place it aside.

New Impeller Body
Install the shaft seal, any studs and the wear plate. Holding the wear plate in place, slide the new impeller body onto the pump shaft. Apply Teflon grease (in a pinch, use dish soap) to the impeller. Match the flat in the impeller center to the flat on the macerator shaft and squish-bend some of the impeller vanes while pressing down to seat the impeller.

New Macerator Body
Match the flat on the hole in the wear plate to the flat on the shaft and slide it on. Do the same for the chopper blade. Lock the shaft as indicated above and tighten the blade’s nut. Match the cutout in any of the gaskets to the cutout in the body. Mount the housing, matching the opening in the housing interior to the openings in the gaskets and pump body. Hand-tighten the screws, and reinstall and open the seacock.


Use a solution of bleach and water to decontaminate your work area. Dispose of any parts contaminated by human waste carefully and properly. Enjoy the benefits of your newly serviced pump.

Quick Tip: Stiff hoses can be made more pliable and easier to remove by ­applying heat from a heat gun.


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