Engine Driven Watermaker Pump

[SailingAdrift]

Hi all,

Does anyone have any experience with an engine driven watermaker pump? Seems like a nice little solution to a Genset to get decent output while charging batteries/ motoring, etc....

Any thoughts would be great!

[Tellie]

Don't do it. There is a reason the major watermaker companies don't build engine take off watermakers. Yanmar will cancel any warranty on their motors thatthey see a high pressure pump mounted to.

[SailingAdrift]

I assumed it was because most sailboats engines are smaller sized. Ours is a 115 horsepower turbo motor sailer.... Does that make any difference?

[slug]

Originally Posted by SailingAdrift

Hi all,

Does anyone have any experience with an engine driven watermaker pump? Seems like a nice little solution to a Genset to get decent output while charging batteries/ motoring, etc....

Any thoughts would be great!

It sounds do able

You would need some kinda clutch
I don’t think a pressure pump is continuous rated , overheat ....then what to do with pump output when you don’t need water

The environment inside a gen sound enclosure is hot and space Is limited

You might need to keep an eye on engine load rpm to maintain de correct ac voltage output


Bow thruster Hydraulic pumps are frequently powered by the generator pump on , ac output disabled

[Lepke]

I had a hp pump on a 4108 running a 10kw generator. I thought it was a good idea at the time. But you run into the problem of light electrical load and the generator engine just spinning for the hp pump. I rebuilt the engine once from the po running light, I didn't want to do it again.

[Pizzazz]

Not impossible to do but really not worth it. Watermakers do not take that much power (about 4 Ahrs/gallon of fresh water), so you are not saving that much. The flexibility and simplicity of having a separate pump/motor combo it worth it.

SV Pizzazz

[phorvati]

Originally Posted by SailingAdrift

I assumed it was because most sailboats engines are smaller sized. Ours is a 115 horsepower turbo motor sailer.... Does that make any difference?

Its complicated. I drove a cat 290 off of atomic 4 for a number of years, thats a 30HP gas engine. Then the same cat 290 off of westerbeake 4-108. Companies don't make it because engine driven RO cannot be made idiot-proof and its not profitable. Its a hassle. But if you are willing to put something together yourself, and own it, it works pretty good.

Off of generator or via 110V AC pump would be even better as you tend to run generator more often and it doesn't hurt you like running main engine at anchor. And membranes need running water otherwise they collect growth.

[CassidyNZ]

An engine driven watermaker pump means you only run it when the main engine runs. That in itself is not necessarily an impediment but there are some issues with the engineering. One of them is the need to clutch the pump so that it isn’t always running. I know some will say “use an aircon magnetic clutch” but my opinion is that it will not be strong enough to run a pump with decent output - that depends on your water-production expectation.

The next best thing is a simple dog clutch that is engaged/disengaged while the engine is not running. But they’re also not that simple to engineer reliably.

I recognised that my main engine would need to run while making water so I added extra electrical generation to the engine so that I could use a 110v, 1.5hp electric motor to drive a CAT pump. I make 90l an hour while extra electricity is being put out by one, two or even three alternators if needed.

With my electrical setup, I can run the watermaker on the batteries for an hour or two in the morning if a sunny day is expected, the solar array will put back the energy. But normally we only make water while we’re motoring.

[bcboomer]

Google it. https://www.echotecwatermakers.com/index.htm
And others.
I think it is a good solution if you have the space.

[Ivansgarage]

Originally Posted by SailingAdrift

Hi all,

Does anyone have any experience with an engine driven watermaker pump? Seems like a nice little solution to a Genset to get decent output while charging batteries/ motoring, etc....

Any thoughts would be great!

Basically a pressure water pump is the same pumps used for water makers...

google "pressure water pump" "pressure washer" membranes need around 750 psi to push water through the membrane... it all adds up to how mechanical are you...

Here is a good link http://sunpurewatermakers.com "piece meal "

Gas driven: SOLD 20 TO 40 GPH GAS DRIVEN WATER MAKER/DESALINATOR – SUN PURE WATER MAKERS

[Tellie]

Be careful on the advice you take. I make a very good living off of bad advice.

[blueblaze]

Hi,

I have been running one for 14 years and have built three others on friends boats. It most certainly works. As to warranty issues you will have to check on that. I have a Yanmar and had warranty work done at the time but that was 14 years ago. Yanmar makes a PTO pulley you can get from a dealer.

They sell clutches specifically built for pressure pumps that are used in car washes. Any pressure pump supplier will be able to recommend one for your situation.

There were articles in Good Old Boat magazine years ago that outlined all the details. There were also a few websites/blogs that had write ups. I have a copy of the magazine hidden somewhere I believe.

We have over 5000 hours on our engine and have been cruising for 13 years. We have had very little problems and no engine issues from the install. The load is really no different than another alternator or engine driven fridge.

It may no be the solution for everyone and solar gets cheaper everyday, but if you will using the boat a lot and running the engine it is an option.

Jason

PM me if you have any other questions.

[walidada]

I have an Echotec system driven of Yanmar 4JH 47 hp making 80 letters an hour. Driven from a supplied Electric clutch to the compressor. Just get the engine between 1700-2100 revs and then booster pump then move the clutch in. Two switches.
I have had it now for four years in the Med and it has never ever given any problem either itself or the motor and it does still 80 litres per hour.
Let me know if there are fundamental problems I have been lucky to miss.
Echotec are giving me live servicing advice when we open up.
Walidada - S & S Swan 47. Based in Scarlino Italy.

[a64pilot]

Most likely you will have to very closely monitor and control engine RPM to maintain an exact pressure as at least my watermakers pressure is controlled by a needle valve, and that works great, so long as the pump RPM is constant and never changes, add to that it’s more than pressure too, you need a pretty precise constant flow rate, to make a half gallon of water a minute, I need a water flow rate of 1.6 GPM.
So most likely your dreams of motoring along and making water aren’t going to work, you will need I believe to maintain a steady correct RPM.

Then the biggest question is why do it? If you want to home brew a simple watermaker, a Honda generator can make 30+ gallons an hour and have plenty of power left over to charge batteries, and it doesn’t put any additional hours on that expensive turbo Diesel.

[walidada]

Thanks. Yes I make sure the revs are constant, but not necessarily the same although it doesn't see to make a difference to the production. I installed it because of the electric consumption. I Have 650 amps of Battery and two Alternators putting out a real 75 amps. Add to that auto pilot and freezer and fridge it seemed too much of a load and I didn't want the constant worry of controlling the battery amps running all these together. One hour per day is more or less enough to fill the tank with a normal crew. I get the point about the Honda butI have tried to avoid a genset and being a classic boat watch the looks a lot !!
Many thanks.