ac pump issues

[paradigm_dog]

I have a 1988 36' mariner aft cabin. The pump for my ac units isn't working correctly. The macerator on the pump turns very slow to where its not pushing any water through the lines.I removed it and took it to a shop and had it bench tested. Works perfect and shows no sign of wear. I cleaned the strainer on the inlet after the ballcock. When the pump turns on it stops running after about 30 seconds. I'm wondering if anyone has any suggestions on what could be causing this to not work.

[paradigm_dog]

Just to be clear my boat is a 3607. Thank you to anyone who is able to help.

[AaHubb]

You might have a clogged thru hull (no water coming in). The AC may sense this and shut off the pump. I have also heard some AC systems need to be primed to get water flowing. Use a garden hose to back feed through the discharge thru hull fitting.

[MissWhit's]

Paradigm_dog,
I can help but need more information. You state "The macerator on the pump turns very slow", this is misleading to me as Poop tank pumps have a macerator and AC systems have a centrifugal pump. Yes, centrifugal pumps are not self priming but the amount of water pressure coming through the petcock/strainer will be enough to force water to the pump so priming should not be an issue. You say the pump stops running after 30 seconds, do you mean the motor actually quits running? Can it be reset with a power cycle to the pump with the same results after 30 seconds? It sounds as if an internal overload device, wether it be temperature or current is kicking in. I would check and make sure you do have water flow from the thruhull fitting/strainer to the pump. Shut the valve off at the thruhull fitting and remove the line from the pump INPUT. Now open the valve and verify actual water flow. It should be very strong/good flow. Next is to be sure you actually have the water connected to the input and not the output. If you can run the pump on a bench with no load and it is ok then something is overloading it. The use of a current probe on the motor wires would show too much of a load. There should be a data plate/label on the motor to see full run load amps.

[AaHubb]

Or, the pump may be fine. You should verify that it is getting power after it shuts off to make sure that the AC unit isn't at fault (assuming that power to the pump is supplied by the AC).

[waybomb]

Or, the pump may be fine. You should verify that it is getting power after it shuts off to make sure that the AC unit isn't at fault (assuming that power to the pump is supplied by the AC).

This!
First make sure each ac unit sends power to the pump

Your Aft Cabin is probably like my Mariner - a couple of ac units use a single pump.
Somewhere on your boat is a relay box that takes the pump signal of either ac unit and directs power to the pump.
On my boat, it is inside the galley cabinet under the sink.
Make sure the power is making it to the relay box.
Then check the power coming out of this box to the pump, and then again at the pump.

Your aft cabin may have it there, elsewhere, or maybe not even have one.

Another point to consider - a pump is doing the most work when it is pumping fluid at its design load. A pump moving less water uses less energy. I doubt the issue has anything to do with load. Also, if your pump is anything at all like every pump on every boat I've had, the impeller is not directly connected to the motor - it has a magnetic coupling. So, even if the pump impeller is locked solid, the motor will not be affected. I think you have a wiring or a relay problem.

Good Luck.

ps - I think your Aft Cabin is simply called an Aft Cabin (3607). A Mariner(3697) is a completely different boat.

[Ozarkkid]

If I may gentleman,
On a related question, Can someone tell me what model or even a part number of a correct filter/strainer for the water system (before the pump) for a Carver A/C. Im a new member and a new/used 1976 carver 33 owner.
Thank You in advance.

[waybomb]

Not sure what you have, but most are simply a Groco strainer basket type unit, similar to what is for your engines, just smaller. Usually has a clear or somewhat clear plastic bowl so you can see debris in the screen basket.