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Reverse Cycle difficulties

Oct 26, 2008
4,902
Catalina 320 Barnegat, NJ
I have a Marine Air 12 K BTU unit and not sure of the age. I used AC in the summer and heat later in the fall last year. I wasn't sure if the reversing valve was working at first when I started using the heat, but eventually it worked fine last fall. I read that reversing valve may tend to stick.

Saturday, we were in the low 50's so I turned on the heat. I made sure the valve at the thru hull was open. Stupidly, I didn't verify that the water was pumping and I left the boat for about an hour. When I came back, no heat was generated and it was obvious that the water wasn't pumping. The pump was still running and very hot to the touch. I shut down and put it out of my mind for the time being.

I painted the surface of the strainer with bottom paint, but I was sure not to clog the openings, at least I think they were not affected! Any thoughts on where to go from here? I'll remove the hose to make sure water flow in the intake is good. I'm concerned that I ruined the pump. Can the pump be replaced without replacing the entire unit? Any thoughts welcome!
 
Sep 25, 2008
6,185
Alden 50 Sarasota, Florida
Make sure the pump is primed before testing it and yes, you can replace just the pump if necessary. The March pumps supplied originally with MarineAir units were not the best.
 
Apr 8, 2011
409
Hunter 36 Deale, MD
Make sure the pump is primed before testing it and yes, you can replace just the pump if necessary. The March pumps supplied originally with MarineAir units were not the best.
Interesting you mentioned the marginal quality of the MarineAir pump. 3 years ago when I first bought my boat I forgot to open the thru hull, which resulted in the unit not being able to pump water and an error code. I quickly realized the thru hull error, but the pump wouldn't prime and kept shutting off and throwing the error code. I was so new to the boat I had no idea how to fix that myself, so I called a marine HVAC tech. He fixed the priming problem in (I'm sure though I wasn't onboard) VERY short order, but also did an inspection of the system and the coolant. He advised me that at some point I'd want to replace that pump as it was of marginal quality.

Long way of adding another data point to Don's comment, but there ya go.
 
May 17, 2004
3,267
Beneteau Oceanis 37 LE Havre de Grace
Make sure the pump is primed before testing it
:plus:

Ours is not self-priming at all, and not especially easy to prime. There’s a bleed valve just downstream of the pump. We need to open that while the pump is running and wait for a good stream of water to come out there before it’s really primed.
 
Jun 15, 2012
585
Hunter 50 AC St. Petersburg
I replaced a "wet end" for my March pump a few months ago. It started leaking from the driven side (where the magnet is) and could have sunk the boat. The pump was not being used at the time and had not been run for many months. Running dry for an hour may have damaged the wet end. I would order a spare wet end and keep an eye on the the present one for leaks.
 
Apr 8, 2011
409
Hunter 36 Deale, MD
:plus:

Ours is not self-priming at all, and not especially easy to prime. There’s a bleed valve just downstream of the pump. We need to open that while the pump is running and wait for a good stream of water to come out there before it’s really primed.
I've discovered an easier way on my boat to prime the A/C line if needed. The PO teed the anchor washdown off the A/C thru hull. If I lock the hose nozzle open so the washdown pump is pulling water through the thru hull and spraying out over the bow, then go back and turn on the A/C, it will prime successfully.
 
Feb 14, 2014
5,421
Hunter 430 Waveland, MS
I did not open a seacock ONE TIME.:mad:

After that, added my 9 seacocks to the

Boat Preparations List

Save $$ and time with one.:biggrin:
Jim...

PS: Use that List in Reverse when leaving your boat.
 
  • Ha
Likes: tfox2069
Oct 26, 2008
4,902
Catalina 320 Barnegat, NJ
Thanks all! Did not realize that priming was going to be an issue. I would guess that the unit is mounted below the waterline, but I will have to look more closely at that. Good to know that I can replace the pump. I will have to take a closer look at all of the components and how they go together. Last year, after acquiring the boat, we used the AC & heat from time to time but I did not really pay much attention to how it actually performs. I couldn't tell you if the P.O. spent any time priming the pump when the boat was put in the water. That day is a bit of a blur to me now!
 
Sep 25, 2008
6,185
Alden 50 Sarasota, Florida
Thanks all! Did not realize that priming was going to be an issue. I would guess that the unit is mounted below the waterline, but I will have to look more closely at that.
The pump location above or below the WL is not an indicator of the necessity to prime it. Centrifugal pumps lose prime easily and always when the boat is hauled and sometimes when heeled excessively.
 
Oct 26, 2008
4,902
Catalina 320 Barnegat, NJ
With no water flow did your marine airrr unit throw a HPF code? If it didn't then you may have bigger problems.
It may have, I don't recall. I came back to the boat, looked for and noticed no flow, shut it off and immediately went to the back to check on the unit. The unit panel was just hanging loose because I am modifying the teak backing, and I didn't really glance at the unit panel. It may have had a code before I just shut it all down. I think I just threw the switch on the AC panel as soon as I climbed in the boat.
 
Oct 29, 2016
1,697
Hunter 41 DS Port Huron
Hope all is well with the unit after you get the flow issue sorted out, I have a feeling its going to be a hot summer
 

Ward H

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Nov 7, 2011
3,014
Catalina 30 Mk II Barnegat, NJ
I have a buddy who replaced his AC water pump one spring because the original one was not running. The new one also didn't run. Turns out the water pump was not hard wired to the controls. Someone had put a plug and socket in the line and it was Un Plugged! :banghead:

At least for Webasto AC units the water pumps are not self priming. Install instructions stress that the intake thru hull must be installed 1' below the max heel water line. The strainer and the pump are to be mounted below the water line.

The KoolAir seawater pump that comes in the Webasto raw water kit is supposed to have "run dry protection" that shuts it down.
I found the best price of $209 for the Koolair PM500 on Amazon.

Just some ideas.
 
Feb 14, 2014
5,421
Hunter 430 Waveland, MS
It may have, I don't recall. I came back to the boat, looked for and noticed no flow, shut it off and immediately went to the back to check on the unit.
HPF code means HIGH Pressure on the Refrigerant Side and your compressor shuts DOWN to protect itself.

High Pressure Freon, so to speak.

The principle cause is Low sea water flow.
Jim...
 
  • Helpful
Likes: Ward H
May 10, 2004
225
Hunter MH 37 Manitowoc, WI
Make sure the through hull is closed. Check the suction strainer and make sure it is clean. Disassemble the pump. There should be 4 wingnuts that open up the pump casing. Carefully remove the impeller. The pump uses a magnetic rotor. Make sure it is clean, as well as the inside of the casing. My pump sometimes gets full of sludge, which prevents the impeller from rotating. It may also get gummed up by the antifreeze.
Reassemble everything. Open the through hull and loosen the strainer enough to vent and fill the suction of the pump. Tighten the strainer bowl and make sure there are no leaks. Then start the system.

This has become part of my spring commissioning and I usually have to do it part way through the summer.
 
  • Helpful
Likes: Ward H

MitchM

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Jan 20, 2005
934
Nauticat 321 pilothouse 32 Erie PA
i fried my march pump, the rebuild kit was $$$ and i got a new march from Depco for a reasonable sum. i made sure pump had prime by cutting in to the h 2 0 line and adding a capped t fitting into which i could add h 2 0 with a funnel . open seacock supplying march pump 'below wate line, march should fill w h 2 0, water should come up close to the level of my T fitting. if not the pump isnt primed , so add h 2 0 .
 
Oct 26, 2008
4,902
Catalina 320 Barnegat, NJ
It doesn't seem that the pump is the issue for now. Friday it was hot in the afternoon so I turned on the AC and the pump pumped and the AC churned out cold air. I didn't have to do anything to prime the pump. I let it run for almost an hour.
The first time I used heat last fall, I had the same symptom with the pump not circulating water. But later in the fall, the pump circulated water and heat came out the vent, and I had no further issues for the remainder of the season. I read that there is a "reversing valve" that was notorious for sticking, therefore it is recommended to run heat periodically just to keep the valve functioning properly. Since I only used heat at the end of last season, I assumed that the valve would be in the heat position when turning it on for the first time a week ago when we had temps in the 50's and I wanted heat. I suppose that may not be the case.

I'm assuming right now that the "reversing valve" may have something to do with the pump circulation and I am also assuming that I need to learn more about servicing this piece of equipment if I expect it to last.
 
Feb 26, 2004
21,702
Catalina 34 224 Maple Bay, BC, Canada
A "reversing valve" is part of the refrigerant system, not the water system. Think of it this way, Scotty: take a window air conditioner - it blows cools air in and hot air out. Then, during the winter, you simply take the window air conditioner and reverse it, so the hot air blows in and the cold air blows out. That is all a reversing valve does, but it does it all inside the unit. So you don't have to open the window when you turn it around, and drop the unit down on your mailman.