March AC Pump

[Mayor]

Ad the lines open. Pump appears to run but no water pressure out of outlet. Just a trickle. Suggestions, please?

[pumpcity]

It's possible that you have one of the following:
1. March pumps create very little head. A small obstruction can reduce the flow rate.
2. Air binding in the pump. Shut the pump off, bleed air/water near the pump discharge, get water, close bleed, turn on pump. Repeat as necessary to obtain full flow. You may have air pockets in the circ line that have to be bled out.
3. Did you have the pump out for repair, or lines disconnected? You may still have air in those lines. Or is a valve inadvertently closed?

[AnchorageGuy]

Or the shaft is spinning but the impeller is not. A common problem. Chuck

[Mayor]

Originally Posted by pumpcity

It's possible that you have one of the following:
1. March pumps create very little head. A small obstruction can reduce the flow rate.
2. Air binding in the pump. Shut the pump off, bleed air/water near the pump discharge, get water, close bleed, turn on pump. Repeat as necessary to obtain full flow. You may have air pockets in the circ line that have to be bled out.
3. Did you have the pump out for repair, or lines disconnected? You may still have air in those lines. Or is a valve inadvertently closed?

Placed a hose from the dock into the outlet hose. Water flow occurred and plenty of clear water through discharge. Pump has 115vac to it. It feels like it is running. No high volume at discharge outlet. Does it need priming? Cleaned the strainer with no change.

[Mayor]

Originally Posted by Waterwayguy

Or the shaft is spinning but the impeller is not. A common problem. Chuck

If the impeller is not working, can it be replaced?

[AnchorageGuy]

If you have allowed the pump to either run dry or the water has flushed out of the system this happens any time you clean the strainer or haul the boat, the pump needs to be primed. If the filter and pump is below the waterline, you will need to disconnect the intake hose from the AC unit, let the pump run until you get water, shut it down and reconnect the hose. That should do it. If not you will need to pull the cover off the impeller and check it. Chuck

[pumpcity]

Waterwayguy had a good point. The impeller is magnetically coupled to the motor. If the impeller is jammed it won't rotate. The impeller is available as a separate item from most pump houses. But first I'd pop the housing (I think 4-6 screws) and see it there is any junk in the housing. Then I'd remove the suction piping so you can sight down the suction inlet and bump the motor for a half second to see if the impeller rotates. You mentioned that water flowed on the hose from the dock. I assume it flowed more when the pump was running than when it was not. If water flows, then your pump is primed. That means that the trickle is a blockage, or when you put the system back together you are introducing air into the system and it's getting back to the pump as it recirculates. Can you describe your system setup? I would wait on pulling the pump apart if you get flow on the dock hose with the pump running and no flow on the dock hose with the pump off.

[chrisjs]

I have this problem repeatedly. I have found that even a small amount of air in the inlet strainer head is enough to cause the pump to not prime. I now know that after traveling, I should release air from the top of the adjacent strainer by loosening the cap. The pump then runs just fine. Provided we do not move the boat, the system usually runs OK. I think air gets entrained as the boat moves through the water. Problem is I do not feel comfortable running the AC/heat while underway, though this is usually not a problem. I would check for an air space first. It is the easiest thing to fix!!

[Mayor]

Originally Posted by chrisjs

I have this problem repeatedly. I have found that even a small amount of air in the inlet strainer head is enough to cause the pump to not prime. I now know that after traveling, I should release air from the top of the adjacent strainer by loosening the cap. The pump then runs just fine. Provided we do not move the boat, the system usually runs OK. I think air gets entrained as the boat moves through the water. Problem is I do not feel comfortable running the AC/heat while underway, though this is usually not a problem. I would check for an air space first. It is the easiest thing to fix!!

Thank you. I will open the strainer to release air with the pump off and try that approach.

[Mayor]

Originally Posted by Mayor

Thank you. I will open the strainer to release air with the pump off and try that approach.

After trying all of the different recomendations I removed the pump panda tried it with negative results. Replaced it with a CalPump and it pumps very well. I guess the March pump was tired. Thanks to all of you who assisted with very good and logical suggestions.

[S/V Alchemy]

As I have a March pump for my Mermaid Marine Air heat/AC, I will take these suggestions to heart.

I've never had problems, but if I do, I now have several strategies. Thanks.

[s/vPainkiller]

Related issue. I think my Dometic AC recirculating pump has died. No signs of life at all. Going to replace it. Any issues with either March or Cal pumps? The new Dometic pumps are very high and I believe I can match the spec and get a reliable pump for much less. Cal pumps are being sold by TheBoatStore on ebay. I need a 1000 GPH pump. Any ideas or problems with this approach?

Thanks,
Scott

[AnchorageGuy]

Originally Posted by s/vPainkiller

Related issue. I think my Dometic AC recirculating pump has died. No signs of life at all. Going to replace it. Any issues with either March or Cal pumps? The new Dometic pumps are very high and I believe I can match the spec and get a reliable pump for much less. Cal pumps are being sold by TheBoatStore on ebay. I need a 1000 GPH pump. Any ideas or problems with this approach?

Thanks,
Scott

Scott, We buy ours from McMaster-Carr. We use the Little Giant. Saves a lot of money and they seem to last a long time for us. Chuck

[Hudson Force]

Originally Posted by s/vPainkiller

....................... Any issues with either March or Cal pumps? ..................

I had a March Pump supplying water for my two AC's on my '73 boat that I bought in '85 and it continued to serve me until 1997 without a problem,- 24 years on task. In '97 I bought a Cal Pump and another in '98. In 1999 I bought my second March Pump that is know working well in it's 13th year of liveaboard use.

[Mayor]

I replaced the March Pump with a 920 gal/ Cal Pump. Works like a charm and it is less expensive that the March unit. I purchased On-Line from Miami. Pumps last a while but eventually they give up also.