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