March A/C water pump

[Full Moon]

I have just burned up the second March pump in the last 2 years. I keep the strainers relatively clean so there shouldn't be a heavy drag from that and the pump is not a direct drive anyway.

Any suggestions for alternates or ideas why these are failing?

 

[Paul45c]

I'm afraid those March pumps are just like that -- I used to have one on my 45c and suffered pretty much the same short life. I'm personally a fan of Oberdorfer, but they're darned proud of them.

 

[Boatsb]

What size march?

I had one go out because the PO put in a smaller one than needed. Can't blame the pump for that.

 

[SKYCHENEY]

I have wondered why they use a magnetic drive pump for the AC units. They have no torque, and break down easily.
Has anyone looked into this, or does anyone know why this pump is used. There much be a logical reason, I think.

Many of the Hatts with multiple a/c units had a big bronze Oberdorfer pump that was direct drive from a 5amp 220v motor. I see no specific reason for that little March pump except that is what Cruisair was using at the time.

 

[Brian Degulis]

I have wondered why they use a magnetic drive pump for the AC units. They have no torque, and break down easily.
Has anyone looked into this, or does anyone know why this pump is used. There much be a logical reason, I think.

The idea behind the magnetic drive is there are no seals to fail and it's easy to replace the wet end. The problem with them is not the magnetic drive it's just a light duty cheap pump with a vented motor they do make one that uses TEFC motor but it's much more expensive.

For sure a bronze centrfigual pump with an industrial duty TEFC motor is going to last a lot longer but also cost a lot more.

Brian

 

[Mike36c]

When you say burned up are you speaking of the motor or the pump end? The water cooled March pumps have a lackluster record but I've had great luck with the aircooled. I have a single March AC5CMD feeding 3 systems that has required zero maintenance since install.

 

[jim rosenthal]

What is a TEFC pump?

 

[Boatsb]

Totally enclosed Fan cooled

 

[GOLE IV]

The key with the magnetic drive pump, is that does not tolerate running dry, zero tolerance.
Make sure your pumps are below water line.
Mine has been running for more that 15 years since install, Only maintenance has been replacing the magnetic impeller. If you let the pump sitting idle for long, long periods, the casing on the impeller trend to fail.

 

[GOLE IV]

BTW - if it is the motor is failing, check the contact on the a/c relay's to make sure the full juice is getting to the motor. Low voltage increases current and heat loss.

 

[Full Moon]

Update. I took the pump apart and everything seemed to be turning free. I took it to my local shop to have them test it and they found some kind of deposit in the cooling lines. They blew it out and hooked it up and everything worked fine. I re-installed it with new hoses and clamps and got it all reconnected. Just as I was finishing up, I had my hand on the strainer basket and went to put the screw on the control box and got a good ZAP. I had noticed a tingle before, but this was a good one. I had been down there in 100+ temps for quite a while and on the boat by myself so all I wanted to do was get out, get a cold beer, clean pants and offer up some thanks for not getting really screw up.

Looks like it is time to call in a professional to help track down this electrical problem. The A/C works fine now but I can't tolerate having such a shock hazard.

 

[Traveler 45C]

While your waiting for your tech, I think it would be wise to shut down power to the entire system and don't run it till the problem has been fixed. Open the breakers.

Since you don't know what's broken you don't know what's being effected. Best to be safe.