How to activate the AC seawater pump in a 53ED

[Streff]

Well, we just stepped on a new to us 53ED. To avoid any issues, the owner had shut off the seacock and turned off the AC & seawater pump breakers. I opened one seacock in the Port engine room (the manual insinuates that there are 2 seacocks), turned the AC pump & AC breakers in the Port engine room. I don’t hear the pump come on or feel sea water flowing. The AC unit is energized so I am just running it on Fan for now. The original manual says to turn a breaker in another panel with respect to the AC pump, presumably in the pilot house with respect to the shore-power breakers? Is there a second seacock to open for the AC seawater pump? Is there another breaker to turn Any input would be much appreciated. PS. The real work starts tomorrow, cleaning the bilge its filled with water & engine work. My wife noticed water under the carpet on the SB back corner of the master suite. None of this showed up on the survey. Streff

 

[Pascal]

If you have a single pump for all units there will be only one seacock.

Usually the pump will only turn on when a compressor kicks in so if younger in fan only mode, it will not run

Now keep in mind that over the course of 40+ years these boats have usually been modified so things will vary

 

[madhatter1]

A call for heat or cool on any unit should switch the pump on.

 

[SEVEN]

Make sure the strainer is clear of all debris. Before you put it back together, open the sea cock, and make sure water is flowing. Once you put it back together, turn the unit to run and then check the hose that is running from the seacock to the units. Unless it’s wire reinforced, it could collapse and you will not get any water running to the units.

 

[SEVEN]

As far as the water in the master, it could be numerous things. Check the rudder shafts to make sure that they are not leaking. Check the shower sump to make sure that it is pumping water overboard. When I purchased mine, the hose that evacuated the water from the sump pump was split in four areas and the water just came right back into the boat. Also check the hoses for the drain in the rear of the boat. The head pump is also back there and could be leaking. Finally the sink annd ice maker anbove could be leaking. Isn’t this fun?

 

[SKYCHENEY]

On my 53ED, there is one pump feeding a manifold to all of the A/C units. The breakers to all A/C's are on Ships Service 2 so make sure you have power there. The panel is in the port engine room. Once you turn on an A/C, the pump will not run until the compressor starts. There is a PWX box in that port engine room that runs the pump. If the pump won't start, it may be a bad trigger. Try starting another AC unit and see if that starts the pump. If none them will start it, it could be a bad triac or a bad pump. You can by-pass the triac and triggers in the PWX box to see if the pump will run.

 

[rwaldrop13]

I had recurring issues with the Crusairs that were in Pau Hana when we first bought her blowing the relays for the pump activation. When I replaced the Crusair split systems with the first 2 MarineAire units, neither one reliably activated the pump(s) on demand. The aft AC unit was the worst, it never actually worked at all right out of the box. I talked to a couple of the vendors in the area and both of them recommended putting the pumps on their own breakers and continuous run. This gave me a couple of advantages, 1) I didn't have to worry about the pumps not getting turned on, or getting off/on chatter and burned out by a bad control relay, 2) I could watch discharge and decide if I needed to clean strainers sooner than expected.

While I understand the mindset of letting the unit turn the pump on as needed, I also had fewer issues with continuous run, better peace of mind and could manage strainer maintenance more easily. The only time I had a problem, one of the pumps sucked a jellyfish all the way thru a strainer to the impeller head where it jammed up.

 

[Pascal]

On a boat with multiple air cons like most hatts, you pretty much always have at least one unit calling for the pump to run so running it full time is ok. The only thing you loose is pump protection if it gets clogged. With the relays when condensers shut down on high pressure the pump will shut down.

 

[SKYCHENEY]

On a boat with multiple air cons like most hatts, you pretty much always have at least one unit calling for the pump to run so running it full time is ok. The only thing you loose is pump protection if it gets clogged. With the relays when condensers shut down on high pressure the pump will shut down.

Or just fix it right and run it as designed.

 

[Streff]

Thank you all for the great input and ideas,I followed some of the comments provided to troubleshoot the issue. Here is what I found, the AC pump has it’s own breaker and it is only triggered by any one of the AC units. I only wanted to run the Aft (owners stateroom) AC.. 2 things were at play.. 1. The SMXi unit was unresponsive.. temp was set at 69 & fan running but no cool air. I did a factory reset and it started to work fine. 2. The overboard water flow when the Aft AC is running is much lower than when the galley AC, for example, is running. To add to this I was standing right outside the PS pilothouse which apparently pushed the discharge opening underwater so I could not clearly see water flow. I was doing this at 1am with a flashlight. At the end, I decided not to risk it, opened all windows and ran the fan only. Luckily, it was not an overly hot night. As we are hoping to travel to the Bahamas in a few weeks, I spoke to an AC tech to possibly add a second AC pump to switch to in case this one stops working. His recommendation is to buy a backup pump instead of adding another pump due to space restrictions. He does not know which pump is on board so I need to research that as I cannot find any markings on the current unit. The space is tight but I think I can take off and install a new unit if need be.Again, many thanks for the advice and responses,Streff

 

[rwaldrop13]

Post pics of the pump, maybe we can help identify. Just for reference, I was really happy with the service and prices at Best Buy Pumps

 

[carolinacoast]

We have the same boat as Sky. Ours is also plumbed with 1 pump for all 4 AC compressor units. Our AC totals 61000btus, so 20.5gpm is the calculation. 1500gph is ideal. We have 2 pumps plumbed in and 2 strainers. I prefer the March pump TE-5.5C-MD. Part # 0151-0124-0100. Slightly over at 1800gph, but a dirty bottom or strainer happens. My backup is an oberdorpher that lasts 2 seasons due to electrolysis, if primary.

 

[rwaldrop13]

We have the same boat as Sky. Ours is also plumbed with 1 pump for all 4 AC compressor units. Our AC totals 61000btus, so 20.5gpm is the calculation. 1500gph is ideal. We have 2 pumps plumbed in and 2 strainers. I prefer the March pump TE-5.5C-MD. Part # 0151-0124-0100. Slightly over at 1800gph, but a dirty bottom or strainer happens. My backup is an oberdorpher that lasts 2 seasons due to electrolysis, if primary.

Mal I used the same March pump(s) on Pau Hana. When I installed new single-piece units, I plumbed one pump for the galley/v-berth and midships stateroom, one pump for the aft stateroom. I had not gotten to installing a new unit in the salon. Pumps were good, like you said slightly over, worked well.

 

[Streff]

Thanks a bunch everyone for the input. I appreciate the part numbers for potential AC pumps. I have attached 2 pics of my current AC pump (unknown make/model). A pump that had the same hose configuration and specs with a similar bolt down would work.Thank youStreff

 

[Streff]

Let’s try again photos.

 

[SKYCHENEY]

Thats the OEM Oberdorfer pump

 

[Streff]

Thank you, Sky. Now that I have a brand, I looked it up and they still make these pumps.. different models under the same configuration. I will call them on Monday and see my options.Streff

 

[SKYCHENEY]

Call Depco. They'll fix you up. And rebuild the old one for you too.

 

[Streff]

Thank you very much, SkyI contacted Depco and they knew exactly which pump (109MB) I need and got it sorted out.Streff

 

[Pascal]

I much prefer the March pumps to any bronze head pumps like these oberdorfers. Problem with them is that the bronze impeller and housing erode with time, at best reducing flow and at worst causing a pin hole in the housing. I ve seen this on a number of boats over years even with the very expensive Scott pumps.

OEM 40-50 years doesn’t mean it’s still best in 2025