# Replacing Engine Driven Water pump with electric



## seanreid71 (Aug 12, 2013)

Has anyone documented the variation in water flow from 2000 RPM to 4000 RPM on a Sailboat engine? If i replace the mechanically driven pump with an electrically driven pump tied directly to alternator (only running when the engine is) What flow should i be looking for? Yamnar 2QM15 in the new motor I am looking at dropping into my 30 hunter

Thank you in advance for your assistance

Sean


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## deniseO30 (Nov 27, 2006)

I thnk most people will say "DON"T!" My own thoughts are that 12 volt motors can't run continuously for hours and hours. The water flow varies with the heat increase as the engine speed increases. I think it's around 5 gals a min, don't know actually. The Yanmar will have it's own pump, so I wonder why your thinking you want electric for the pump. Is it for the engine coolant, or the sea water?


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## seanreid71 (Aug 12, 2013)

When I got the engine, the water pump pulley is not there. so I need to find either a new pump or a pulley that will work. New Pump is $400, Electric Pump is $125 Was just trying to think outside of the Yanmar Box

Raw Water (salt)


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## svinshallah (Oct 1, 2012)

I've seen it done especially on gensets or where there were originally multiple pumps. There's no reason it won't work in theory. Most electric pumps are not designed to be run continuously. Those that are can be expensive. Only an example. The little Johnson pump on my refrigerator pumps 1.6L minute and costs about $250.


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## azguy (Jul 17, 2012)

a mechanical pump is simple and will last for a decade, it should be the 1st choice IMHO..


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## Bob142 (May 27, 2012)

Agree with above...If you have an electrical problem you now also have an engine problem...most diesel engines will run without electricity but not without cooling...


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## mad_machine (Dec 16, 2012)

if you can get the dimensions of the pulley, you can probably have one made for less than 400


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## deniseO30 (Nov 27, 2006)

Find out what tractor that engine goes in. for example.
John Deere 332 Tractor Yanmar 3TN66UJ 18HP Diesel Engine Water Pump Pulley | eBay


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## boatpoker (Jul 21, 2008)

svinshallah said:


> There's no reason it won't work in theory. Most electric pumps are not designed to be run continuously. Those that are can be expensive. Only an example. The little Johnson pump on my refrigerator pumps 1.6L minute and costs about $250.


I think I'll call my next boat "In Theory" .... cause' "in theory" everything works.


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## ctl411 (Feb 15, 2009)

Ask around boat yards they may have one used off a blown engine.


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## overbored (Oct 8, 2010)

I would not want electric, the mechanical is to simple, but it would work. although by the time you buy the pump and all the fittings you will be out $200 and thats if you select the proper pump the first time and it does not cause a overheat problem which will not be cheap, Happy experimenting.
they make electric water pumps for many car engines which replace the mechanical. they are use on race engines because they do not rob and power from the engine when run off a battery.


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## arvicola-amphibius (Apr 14, 2012)

As well as the obvious reliability of an engine driven pump, something else to consider is that such a pump delivers a volume of cooling water proportional to engine RPM. The engine manufacturer optimises this.
Proportional flow won't be easy to achieve with a non OEM electric pump, so if you get it wrong you could have too little volume at high revs, or, potentially just as damaging, too much at idle.


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## Maine Sail (Jan 6, 2003)

A couple of thoughts..

#1 an impeller pump is designed to self prime, push into lots of head pressure, eg: the heat exchanger, and works off the direct interaction of the impeller vanes contacting the pump body. These pumps have incredible friction and thus require a lot more hp to operate than an el-cheapo centrifugal style pump eg: Rule style....

#2 The mechanical pump on your engine is designed to give proper flow at varying RPM ranges. At idle for instance you don't want the pump pushing maximum flow or the engine may not maintain a proper combustion/operating temp. An electic pump is either on/off and flow depends upon specs and operating voltage. A pump controller "could" be made but this venture would cost more than the mechanical pump and would need to be engineered to mimic the mechanical pumps RPM / flow characteristics. This woul be a fairly complex built which would require tapping into the tach sense circuit among other things...

#3 An electric ump that can match the performance specs of he the mechanical pump would also need to be an impeller type pump and NOT a diaphragm or centrifugal style pump. The problem with impeller pumps, due to the high friction design, is they will draw considerable current to get to the desired specs.

#4 If this pump is drawing say 15A this 15A comes straight off your alternators charging potential. Let's assume you have the typical 35A rated alt on a Yanmar. This alt will realistically put out about 18-22A when hot. They don't live up to the rating, except for a few moments immediately following a cold start. Now subtract the additional 15A of the electric pump and you are putting perhaps 5A net into your battery bank. In this scenario you've just cut your charging potential by 75%......

#5 most small diesels will run perfectly without an alternator working. If your alternator were to fail your engine is now dependent upon the battery bank to operate. With the mechanical pump your engine is not dependent upon the battery bank to operate unless it has a small fuel lift pump. These fuel pumps draw fractions of an amp however and thus could run for days vs. hours with a 15-20A load.

#6 the mechanical pump only operates when the motor is running, and move only the water it should, based on engine RPM. An electric pump would need to be wired to do the same. If not wire properly, such as improperly wired to "ignition key on", you would run a very high risk of hydro locking the engine. This is when the pump puts too much water thought the system before the exhaust gas presure can evacuate it from the vessel. Water backs ups until it gets into the exhaust valves and fills a cylinder. Water is NOT compressible, and in a worst case, can destroy an engine......


Could it be done "properly"? Probably, but it would be more costly, more complex, less reliable, and would reduce your charging potential by the current load of the electric pump....


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## Ferretchaser (Jan 14, 2011)

You can get a pulley for around 20 bucks and may just have to turn out the pore of it to fit the pump. 
Amazon.com: V-Belt Pulleys - Power Transmission Products: Industrial & Scientific


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## Markwesti (Jan 1, 2013)

First off I would not go the electric pump , although I have thought about it . I was going to use my Jabsco Water Puppy . I had no idea the water flow , but the pump it's self was just like my Jabsco raw water pump . I decided not to reinvent the wheel . On my 2QM15, It's fresh water cooled . The raw water pump needs a impeller and seal in 2-3 yrs. The fresh pump (Yanmar) seems to never need anything. I checked the impeller on the Yanmar pump the other day and it looked new. It was 30 yrs. old ! Ok so here is my advice PLEASE don't read any further if you don't want it . Drop the electric thought . Convert to fresh water cooled even if you are in fresh water . It will be expensive and time consuming. It will also be worth it .


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## Coquina (Dec 27, 2012)

Atomic 4 Fresh Water Cooling System - Electric Antifreeze Pump

Note the electric pump is only for the fresh water circuit.


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## CalebD (Jan 11, 2008)

If it is an Oberdorfer 202 type pump you can find it for less.
Moyer Marine Atomic 4 Engine Rebuilding and Parts
sells them. 
It sounds to me as though your water pump is belt driven though, not off an auxiliary drive. I have seen these pumps used on some Universal diesels though.

Also sounds as though you are missing the belt drive pulley, but I'm not clear on this.


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## bljones (Oct 13, 2008)

seanreid71 said:


> When I got the engine, the water pump pulley is not there. so I need to find either a new pump or a pulley that will work. New Pump is $400, Electric Pump is $125 Was just trying to think outside of the Yanmar Box
> 
> Raw Water (salt)


Something tells me the missing pulley is the least of your worries with this engine, since a missing pulley begs the question, what else is not there?

have you ever heard this engine run?


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## Sails149 (May 28, 2017)

Well this is an old thread but the original poster does not say if it the seawater cooling pump or the freshwater engine pump. It sounds like it's probably the engine driven freshwater cooling pump.
If that the case there are many aluminium bodied pumps availble with 3000 hr rated electric motors used in cars and race engines. Try Jegs.com for lots of choices.
If you want a raw water cooling pump there are good jabsco pumps availble some continuous rated. Here is a old video of a guy who made various modification to improve his Volvo MD21a including using a jabsco water puppy impeller pump. (You need 15 gal/ min for 100hp)
search utube for. "Volvo penta md21 a troubleshooting guide" (I can't post a link) from Hawaiiecom 
Some other good ideas too , and he talks about how to wire up the pump too.
If you are careful then it could work well.
It's a good way to keep an old engine going if parts are hard to come by.
Also I read a story years ago of guys doing a long delivery and lost the impeller pump and used a bilge pump as a back up and ran for 3-4 days like that!
Cheers Warren
Ps just saw it was raw water pump was needed.


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