March A/C pump : liquid or air cooled?

[krush]

I have two liquid cooled 3series march pumps (one for each self contained A/C). My guess is they were installed during refit ~1995 so they are old.

I'd like to get a spare, because if there is spare on the shelf, none will fail. Also, one probably needs a rebuild as it's seems to be a low on pressure. And I'm sure the cooling tubes are full of gunk (the motor casing has a little heat checking).

For the spare, should I get liquid or air cooled? Are the air cooled quieter? This pump does hum/vibrate a little and can be heard in other places of the boat (I think I'm going to foam mount it and isolate the first few feet of hose better).

Many here have great experience with air cooled, but that is more heat to the engine space. We have silty water here when the props churn up the mud, but it's fresh.

 

[Boatsb]

I've had good luck with the air cooled.

Silt and all. Just oil it twice a year.

 

[saltshaker]

Either works fine but I do prefer air cooled. March pumps are pretty reliable and need very little to no maintenance.

 

[krush]

Why air cooled preference?

Air will work fine....it won't get wet in the engine room. And if it does get submerged, I'm having a really really bad day!

Is there a noise difference between the two?

 

[Boatsb]

The water cooled is a sealed pump. The air cooled runs cooler.

 

[krush]

Did I mention both pumps appear to be 23 years old?

 

[Boatsb]

I have one like that in my shop.the old red plastic with tubes.

They work fine. In my world where it's run all (daily) and needed a larger pump the 5 series works well. 10 years and running (knock wood). But I must have done it wrong.

I have 2 cruiser split systems with short hoses to the discharge and have not done anything but maintenance ( flushed every 4 or 5 years) and oiled the 2 spots on the pump every 6 months or so.

 

[Pete]

AC air cooled pumps were not a good choice for me. I bought a fully enclosed fan cooled March magnetic coupled drive with a capacity around 1800 GPH to serve all five units in the engine room. Turns out that most pumps in this category use Class B electric motors which have an ambient temperature rating of 40 C or 104 F. I doubt any of our engine rooms meet that spec when underway on a hot Summer day. Mine is more like 125 F even with the exhaust fan blowing lots of hot air out the hull vent. Needless to say the motor shut down when needed most. I ended up cooling the motor air intake with a small raw water radiator and fan, using a tap off the AC cooling water before the AC units in the flow.

All that to simple say, be sure the ambient air temperature requirements of any pump motor are met where you plan to install the unit.

Pete

 

[racclarkson@gmail.com]

AC air cooled pumps were not a good choice for me. I bought a fully enclosed fan cooled March magnetic coupled drive with a capacity around 1800 GPH to serve all five units in the engine room. Turns out that most pumps in this category use Class B electric motors which have an ambient temperature rating of 40 C or 104 F. I doubt any of our engine rooms meet that spec when underway on a hot Summer day. Mine is more like 125 F even with the exhaust fan blowing lots of hot air out the hull vent. Needless to say the motor shut down when needed most. I ended up cooling the motor air intake with a small raw water radiator and fan, using a tap off the AC cooling water before the AC units in the flow.

All that to simple say, be sure the ambient air temperature requirements of any pump motor are met where you plan to install the unit.

Pete

Serving four units with an 1800GPH March mag drive coupled to a Marathon 1/3HP TEFC rated for 50C. While that still seems like it couldn't handle the ER heat, it hasn't failed in the 18 months I've had the boat. ​wood knocking sounds

 

[bobk]

Are those temperatures max allowed ambient temperatures, or maximum allowed temperature rise of the motors?

Bobk

 

[Pascal]

I ve found the air cooled pump to be very reliable as long as they don't get wet. One problem I ve had was one builder installing the air con pumps under a large shelf with various stuff including the watermaker. One time it popped a leak and salt water dripped from th back of th shelf onto the pumps... duh.

A single pump for the whole boat is a bad setup. I'm adding a second pump to mine with a manifold so I can switch on the fly. Air con isn't optional in so fl and Bahamas

 

[racclarkson@gmail.com]

Ambient

 

[MVCaprice]

March pumps are pretty reliable and need very little to no maintenance.

As long as you don't run them dry!!! It seems like the air cooled motors seem to outlast the plastic magnetic drive pump assemblies. Luckily they are fairly cheap and readily available.

 

[Boatsb]

Mine is air cooled and the pump is plastic mag drive.

 

[MVCaprice]

Mine is air cooled and the pump is plastic mag drive.

Yep. Sorry I wasn't clear. I am speaking of the standard MD-AC-5C pump.

This is basically what I have seen happen when one run's dry....

 

[racclarkson@gmail.com]

As long as you don't run them dry!!! It seems like the air cooled motors seem to outlast the plastic magnetic drive pump assemblies. Luckily they are fairly cheap and readily available.

Couple of nights ago I left the air-conditioned comfort of my boat to have dinner on visiting Hat. When I came back it was blazing hot. The two units I left on high pressure alarmed and shutdown. The main salon unit with two evaps was blowing hot. The high pressure alarm was the clue. The pump was running, but no flow. I'm guessing something clogged the thru hull intake. After turning the pump off for a few seconds and restarting it took off; you could see it had water from the clear plastic discharge line. After allowing the units time to cool down, I restarted and my environment became, once more, sublime. The pump didn't care if it was pushing water or not, just that it was wet. That was good news because as some of you may recall, March Pumps can make a bad pump and may not stand behind it. Caution, strong language:

https://www.youtube.com/watch?v=dZSg4--fCF8

But if it does stop pumping, here's an official Bolivian technical update:

https://www.youtube.com/watch?v=m8CPElV708A

 

[Pete]

My AC water pump motor is a Baldor TEFC with a 40 F ambient temperature rating.

Pete

 

[Pascal]

You should have a relay box so the pump will shut down when the air cons trip. It worth adding

I ve seen a Cooke of cracked impellers over the years, they re really easy to change just pop the screws and install a new one. You don't even have to pull the hoses