Macerator Acting Strangely

[Homer Shannon]

I don't have any way to check the amps at the pump, but it is wired on a 15' run of new, unspliced, #10AWG wire. It is connected to two type 24 batteries showing 13.5V and it behaved the same with and without the motor running when the boat was in the water. I think I've pretty much eliminated any problem with getting good power to the pump.

Also, now that the pump is running again, I'm connected to exactly the same setup and it is working fine.

I noted in the Jabsco instructions that this motor has a 'fifteen minute duty cycle'. Does that mean it can be run for 15 minutes safely and then should be shut off, or does it have some kind of sensor and shuts itself off? I've never run it anywhere close to 15 minutes as my tank is only 20 gallons, but if there is an internal senor, perhaps it could be bad.

[HopCar]

"does it have some kind of sensor and shuts itself off?"

Interesting thought. The following is from the description of the motor used on the Jabsco macerator pump.

"Includes Run-Dry Protection Device

that shuts-off pump."

If there is some kind of sensor it must be built into the motor as it doesn't show on the parts list. Why don't you contact Jabsco and ask them?

[Stu Jackson]

WADR, RTFM. It should say these pumps do NOT like to be run dry and that the switch should be close to the pump so you can turn it off immediately when it has finished emptying the holding tank. I know this because I just bought a new one to replace my 26 year old OEM (going Shurflo instead of Jabsco). Good luck.

[Homer Shannon]

Hopcar: I took your advice and fired of a question to Jabsco (Xylem). Surprisingly, Jeff Lander, a product specialist got back to me very quickly and provided two pieces of information.

First, regarding the 15 minutes of operation and the reset switch:

It means that the pump can be run for 15 minutes safely and then should be shut-off. There is however, a poly-switch that will shut the pump off if you run it dry for a period of time or if the motor/impeller isn’t spinning freely. If there is a blockage or if the impeller is in a set position then what happens is the motor cannot spin freely. This causes the macerator to draw a large amount of current, which trips the polyswitch that turns the pump off to protect it.

This does not quite fit my problem as my pump never shuts off, it just slows to a crawl, but it is good to know.

He also responded:

From time to time the impeller can develop a “set” position. While sitting in the housing, a few of the vanes are always bent over. If the impeller isn’t in great shape or if the impeller sits for a period of time, then what can happen is that the impeller develops a “set.” The impeller “set” can sometimes causes a breaker to trip or in some instances, cause the motor to appear to run slowly (because the shaft isn’t spinning freely). Once the set is “broken” and the shaft can spin freely again, it appears as if the speed of the motor “picks-up.” If you think the macerator is running “slowly” then pop the cap off at the back of the macerator, insert a slotted screw driver and turn the shaft to aid in breaking that set position.

Again, this does not match my situation as I've had the behavior start while I was using the motor - no time for the impeller to take a set.

I guess I'm never going to know exactly what has been going on. I have removed the holding tank and all the plumbing. Before spring it will all be reinstalled with the motor right on top of the tank, in full view and with access to the screwdriver slot in the back of the motor. It will get annual lubrication, the lift height will be decreased and the potential from a deck plumbing vacuum leak eliminated. It may yet fail agian, but I will know exactly what is NOT causing the problem.

Thanks to all the members in this list for your help.

[Homer Shannon]

The problem with the intermittent macerator pump had not gone away when we stored the boat for season in October of 2019. Due to covid and family health issues, we did not launch our boat for the 2020 season. Since I had done a lot of the seasonal prep in the spring of 2020, when we still planned to launch, my list of repairs this spring goes a bit deeper than normal. Included in this list was attacking the macerator pump issue again.

First, I checked the pump to see how it would fare this year. I partially filled the holding tank and ran the pump. Initially, it seemed to be working fine, then it slowed to a crawl and stopped - classic failure as I've been seeing it.

I started pulling things apart, and as usual, there were no clogs, vent failures, loose wires or other issues that would stop the pump. I've long suspected that the problem may be related to the impeller. Could it be binding? Does it need lubrication? I put some high tech lubricant on the impeller and put the motor back together - same problem. Still thinking this may be a binding issue, I disconnected the hoses and loosened the four nuts that tighten the impeller housing and output to the motor. I ran the motor with the nuts loose. It ran strongly. Without reconnecting anything, I thighted the four nuts on the assembly again. The motor stalled.

OK, now I'm thinking that the impeller is most certainally binding in the houseing. The housing and the top metal plate are separated by a thin paper gasket. What if I made a thicker gasket? Looking around the shop, I didn't have much on hand but I did have some sour cream continer covers. These are made of a softish plastic which would stand up well to water and are easily cut. The paper gasket is 0.1mm thick. The plastic cover material is 0.4mm thick.

I made the replacement gasket and installed it. Upon reassembly in the boat, I tested the motor with all the nuts good and tight but no septic hoses connected yet. The motor ran strongly. I then connected the hoses and tried again. The pump drained the small amount of water in the tank quickly without any leaks or other problems. I filled the tank about half full and pumped it out again - no problems at all.

I won't be 100% certain until we launch and start using the pump regularly, but I believe this is the fix. The paper gasket is too thin and causes the impeller to bind on it sides. By installing a thicker gasket, I've given the impeller enough room to spin easily.

I think. I'll report back as the season progresses.

[Captain Bill]

Originally Posted by Homer Shannon

I won't be 100% certain until we launch and start using the pump regularly, but I believe this is the fix. The paper gasket is too thin and causes the impeller to bind on it sides. By installing a thicker gasket, I've given the impeller enough room to spin easily.

I think. I'll report back as the season progresses.

I alluded to the issue of a thicker gasket in an earlier post. I once had to clear a hair clog in my shower macerator and destroyed the gasket while taking it apart and discovered I did not have a spare on board. I made a new gasket out of some automotive gasket material I had on board. The material was almost like a heavy poster board than thin paper. Probably not even 1/16 thick, maybe even 1/32. The shower pump is about a foot above the sump and there was just no way it would prime after putting it back in. I talked to Jabsco and they said that the thicker gasket allowed too much space between the impeller and cover. One thing to consider since we last discussed this topic. I had one fail to prime because of a failed seal around the motor shaft. It's been four or five years since that happened, but if memory serves correctly it was an o-ring failure.

[Homer Shannon]

Yes you did mention this, Capt. Bill. I'd suspected impeller binding but never tried just looseing the four nuts to see if it relieved the condition before. It's a simople test and I should have done it long ago.

I have a very low lift height to prime, so I suspect I won't be "over gasketed", but if I am, I'll look around for some 0.2mm gasket material and see if that is a better fit.

[sailorboy1]

As I read this thread you have been having an issue with a pump now for 8 years. ON THE SAME PUMP! My system is similar to yours and my macerator would normally last 1 year of full time on the boat. Replace the pump already! I have had better service life with the Flowjet macerator.

[chris95040]

WOW. Do you spend all day with a pebble in your shoe, too?

So.. 8 years later and we still don’t know the voltage at the motor terminals when the pump is on and failing, right?

[Homer Shannon]

Originally Posted by chris95040

WOW. Do you spend all day with a pebble in your shoe, too?

So.. 8 years later and we still don’t know the voltage at the motor terminals when the pump is on and failing, right?

There is no problem with the voltage at the pump. That was all settled long ago. The pump has been intermittant all this time - working perfectly for a while then doing this run and then stop behavior. I appreciate all the information I gathered during this time, but no one (Capt. Bill excepted) actually got to what appears to be the root problem. As for the age of the motor, it may be getting old, but it only gets used a dozen times or so a year. It is not corroded, so why would it be too old to continue using?

[sailorboy1]

Because in my experience a Jabasco macerator will have its seal go bad and the bolts that hold the pump to motor corrode within 1-3 years (i have gone through 3 the last 10 years) and it only hapoens when the tank is full, how much time have you spend messing will this drying pump the last 8 years?