Watermaker Replacement Pump & Magnetic Clutch

[Tellie]

I prefer Cat pumps and I think think brass is not the best SS is better. All that being said, I have a brass CAT 3CP model, not sure of the numbers, (I'll find out later today if you're interested) with a 12V dual groved clutch attached and also the rails. I have no use for it has just been sitting in my shop. The pump and clutch are about four years old but neither have ever been used. The whole set up is worth around $600-$750 new. Make me a decent offer.

PS No matter what you do a dual grooved pulley is better. If you set this up right you'll go through less belts.

[chardis]

OK. I sent you a PM.

[chardis]

Of course stainless is better, but for more than twice the price..? My Hawk is coming up to 5 years old and the brass looks fine. I imagine good quality marine-grade brass would be used rather than the cheap stuff. But would you expect a the brass housing to fall apart after 10 years? And would the corrosion be from the outside or the inside? If it's only on the outside then I can just take good care of it and it should be fine.

[Tellie]

The key to taking care of the internals of a brass pump on a DIY watermaker is to always give it a good fresh water flush after each use. As you said it's all about price. Personally I think ten years is pretty much the life expectancy on most all boat systems. But even if you had to replace the entire pump every five to eight years it's not a bad price. The only other plunger pump that I would feel comfortable saying would last ten years and beyond is a Titanium pump. But you can buy a lot of 3CP1120s for the cost of one of those.

[waterworldly]

Just a suggestion, from some advise that was given to me by the master mechanic at a very good yard in Miami: keep it the same. For many reasons, it is often better to bite the bullet and replace your pump with the same model. Everything will be the same, guaranteed, shaft size, mount, clutch, and importantly, output. In a situation where proper pressure is the key, if the pump was matched to your system, it may make a huge difference if there is even a minor output difference, from blowing the whole system to not making the same amounts of gph. Call the manufacturer, they most likely will be able to id the pump you have and recommend the proper replacement. I have followed that advise and after changing most of the pumps on this boat (including the high pressure water maker pump, we rebuilt it ourselves), have not had any issues and the installs went smoothly. Since pumps do not require constant maintenace, why go through all of this to make that maybe once a year oil change a little easier and risk everything else?

[chardis]

Hi waterwordly,

Thanks for the advice, though I've decided to go with the CAT. Reason being that the Hawk is just so damn difficult to buy, service, get parts and everything else.

My watermaker is not a prebuilt system, but made out of various 3rd party parts, and I have controls over the flow and such things. The CAT has slightly higher PSI & flowrate at 1750RPM, it goes from 100-2200PSI. My membranes are rated at 2000PSI, so I will run it lower than 1750RPM and I can check the pressure, turning it up slowly until I get it to 1700PSI or thereabouts, then I will remember the RPM for the pump & how many turns to turn the pressure control to have it where I want it.

[Tellie]

Just a quick and very important correction Chardis. SW Membranes are rated for 1000psi and you want to only pressurize them to 800psi. for them to work properly. This pressure range will also be a lot easier on the CAT pump which will still provide the proper flow rate as well. Remember your pressure will be dictated more by the restricting pressure valve than the rpms of the pump. At 2000psi you'll certainly damage the membranes and also run the risk of rupturing the membrane vessels.

[chardis]

They do indeed say max 1000psi, thanks for the correction.