Steve,

25 year old system — original installation on a 44 foot sailboat.  In North Carolina. One water pump [P500] and two Marine Air CM16H units.  Two, three knob cabin control panels.  Water pump that tees to both units.  Both CM16H units have their own breakers and the water pump also has its own breaker. [I had posted on June 5th, 2011 with separate problem of low water flow that we resolved with new hoses].  Units had been working well since then.  Now both units tripped off.  Checked water flow, no flow at all using either one or other control panels.  Checked seacock, strainer.  Both okay.  Fans working in both units Water pump does not come on.  Felt pump after breakers tripped and it was very hot.  In hindsight I believe I heard the generator 'struggling' when I attempted to restart the water pump by turning control switch to 'start'.  Have relay #2PRP installed.  Opened to inspect.  Fuse was fine.  Found the ground wire for the pump was sort of loose so redid that connection. Checked all other connections.  Tried to start again, fuse blew at that point.  Your thoughts much appreciated.

George

One other thing George…That pump is a bit too small for two 16K units…A P500 is good for up to 24K of A/C…You have 32K.

I know it's been working all this time but since you likely have to replace it anyway I would step it up to a 1000 GPH (next size up)

My pump prices are not very competitive…I buy them from Dometic because they cover any warranty labor if it goes bad in a year (good for me as the installer & guy that has to replace it) but that also raises the price…Kinda like a lifetime muffler…Same product but you pay for the warranty 

The pump you are looking for is either a March AC-5C-MD (Air Cooled & don't get it wet) or a March LC-5C-MD (Liquid Cooled & Submersible) 

Steve~

Yes…Port orientation will be the same…Sound too…But the larger pump will have a 1" inlet (same outlet) that you can get a PVC pipe bushing to reduce to the same 3/4"…It's better to go with 1" but they are bushed down all the time…In fact the pump from Dometic comes with the bushing (not sure about from March) 

As far as the fuse…10 amps is 10 amps…That 500 pump shouldn't draw more than about 2 amps…The LC-5C draws 2.2 amps.

http://www.dometic.com/FileOrg…..0Sheet.pdf

Steve~

Make sure you don't order this pump as it Must Be Submerged to keep it from overheating:

http://www.marchpump.com/5c-md/

Steve~ 

Post edited 8:50 am – July 12, 2011 by Steve Pooler

George~

Glad you are back up & running…As long as you don't get it wet & oil the motor once in awhile the AC-5C-MD March pump will likely be the last A/C pump you ever buy…I can't make any money on those things after I install one   

They can be a ball of rust with the capacitor hanging off the side by it's wires and the darn things still just run…  

Obviously I can't hear it, but gurgling noises can mean the pump head/impeller is cavitating…Could be from a restricted thru-hull or strainer, or from a suction side leak that when running is sucking air in (should drip when off)

You might notice this air or cavitation in the overboard's discharge…They could show as a Milky stream, or Larger bubbles…

As we talked…The new pump has a 1" inlet that you can bush down to 3/4" but it will need every bit of that 3/4" to not cavitate…Hope your thru hull or strainer is not 1/2"…And make sure both strainer & thru-hull are clean…

Also if the strainer is a Perko brand with the 2 wing nuts that hold down the basket cover….Be sure that cover & nuts are tightened equally…If the cover is the slightest bit cockeyed it may suck air…

Airiated water is not as good at removing heat as a solid flow…

Steve~