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Old 08-06-2011, 10:59   #1
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Electric Centrifugal Raw Water Pump 12V

The belt-driven impeller-type water pump">raw water pump on my 35 HP diesel engine is a problem:

1. Impeller cannot be inspected or changed without removing the pump, and the pump is hard to get at.
2. The belt cannot be adjusted without removing the pump, trying a new placement on the bracket, reinstall, and check the tension. (I know this is weird but is the way it is).

I'm thinking about installing a 12-volt electric centrifugal raw water pump to replace the engine-driven pump. I found a 12V stainless steel pump that has the required flow rate and head capacity. It will be mounted with a continuous flooded suction. (I would prefer a bronze pump, but can't find one that delivers 15 GPM at 10 ft head). I'll wire the pump with a relay to energize it whenever the engine ignition switch is "on."

I'll leave the engine-driven pump installed without the belt, with plugged hoses that I can swap out with the electric pump hoses, in case the electric pump fails. If electric pump fails, I'll remove the electric pump hoses, install the engine pump hoses, and connect the belt to the engine pump.

Any words of wisdom or caution about doing this?
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Old 08-06-2011, 11:19   #2
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Re: Electric Centrifugal Raw Water Pump 12V

Welcome to the forum Sagittaire.
10 ft of head? seems like a lot.
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Old 08-06-2011, 11:36   #3
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Re: Electric Centrifugal Raw Water Pump 12V

hmmm, boy I wouldnt switch from the designed pump. If you do, consider putting a snap disc thermo switch on the exhaust, to set off a buzzer or light when your pump fails....
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Old 08-06-2011, 11:39   #4
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Re: Electric Centrifugal Raw Water Pump 12V

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Originally Posted by Cheechako View Post
hmmm, boy I wouldn't switch from the designed pump. If you do, consider putting a snap disc thermo switch on the exhaust, to set off a buzzer or light when your pump fails....
Sounds like a really good idea.
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Old 08-06-2011, 11:42   #5
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Re: Electric Centrifugal Raw Water Pump 12V

I once had a 23ft Searay with a 270hp Volvo-penta V-8, with a crankshaft driven, front mounted raw water pump. Pump came loose from bracket and was in-operable.
Connected submersible bilge pump to raw water intake on engine. Flooded boat sump with thruhull, and brought the boat home on the bilge pump. Every boat I have owned since that, has had that ability rigged up.
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Old 08-06-2011, 16:05   #6
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Re: Electric Centrifugal Raw Water Pump 12V

Replies much appreciated!

James, 10 ft of head includes a 3' elevation gain from the load waterline to the raw water exit on the side of the hull (boat has dry stack exhaust). I'm allowing the other 7 ft of head for the intake strainer, heat exchanger, and hoses. I am also able to exactly measure my raw water flow rate with a bucket suspended under the raw water exit.

Cheechako, excellent point - boat already have an Aqualarm flow sensor and buzzer/light.

Blue, good story.
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Old 08-06-2011, 16:12   #7
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Re: Electric Centrifugal Raw Water Pump 12V

Quote:
I'm thinking about installing a 12-volt electric centrifugal raw water pump to replace the engine-driven pump. I found a 12V stainless steel pump that has the required flow rate and head capacity. It will be mounted with a continuous flooded suction. (I would prefer a bronze pump, but can't find one that delivers 15 GPM at 10 ft head). I'll wire the pump with a relay to energize it whenever the engine ignition switch is "on."
Not a good idea to wire it to the ignition switch, as it will pump water without the engine running and could fill the clyinders. Better rig an oil pressure switch, so as the oil pressure builds the pump comes on. Theres no need from the pump to be running immediately on the engine turning over



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Old 08-06-2011, 16:19   #8
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Re: Electric Centrifugal Raw Water Pump 12V

Keep what you have now and live with it. It will cause you less trouble in the long run. By the way, what engine do you have?
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Old 08-06-2011, 17:22   #9
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Lightbulb Re: Electric Centrifugal Raw Water Pump 12V

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Originally Posted by DeepFrz View Post
Keep what you have now and live with it. It will cause you less trouble in the long run. By the way, what engine do you have?

i dont agree , the OPs suggestion is a better improvement . I suspect his engines a yanmar.??

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Old 08-06-2011, 19:08   #10
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Re: Electric Centrifugal Raw Water Pump 12V

Welcome Aboard CF
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Old 09-06-2011, 07:39   #11
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Re: Electric Centrifugal Raw Water Pump 12V

GoBoatingNow: I have dry stack exhaust so no possibility of filling cylinders with water, but I like your idea of running pump from an oil pressure switch.

DeepFrz: It is an Isuzu "Suzie Diesel" by Klassen, Model 3KR1. No longer made.
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Old 09-06-2011, 08:00   #12
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Re: Electric Centrifugal Raw Water Pump 12V

The reason the original raw water impeller was made and installed by the manufacturer is simplicity, reliablility, and cost. (not neccessarily in that order).

I would not hesitate to install a second pump through a Tee and a ball valve for a backup, but the belt driven pump, although it has known failure modes, (broken belt, bad impeller, clogged sea strainer). The new electric pump also has failure modes that will require a different kind of vigilance, (bad wiring, low voltage, corroded connections, insufficient pressure, loss of siphon, etc...).

The belt driven pump is always on when it is needed. The electric pump needs to be simularly controlled. Advantages of electric pump, can monitor with an indicator light, cheap, easy to maintain. It is up to you to decide what you priorities are, but being able to keep boat operating in case of failure, and detecting failure are high on my list.

Some things come with changes in technology, when your boat was built a good electric pump may not have been available. Do newer engines have electric cooling??? My Honda does. The former belt driven appliances now each have their own built in electric motor, (maybe in prep for hybrid conversion?).
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Old 09-06-2011, 08:12   #13
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Re: Electric Centrifugal Raw Water Pump 12V

Kind of out in left field...but have you considered getting rid of the raw water all together and going with something like a keel cooler http://www.waltergear.com/
Since you already have a dry exhaust, it may be just the ticket...
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Old 09-06-2011, 08:20   #14
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Re: Electric Centrifugal Raw Water Pump 12V

Quote:
Originally Posted by Sagittaire View Post
GoBoatingNow: I have dry stack exhaust so no possibility of filling cylinders with water, but I like your idea of running pump from an oil pressure switch.

DeepFrz: It is an Isuzu "Suzie Diesel" by Klassen, Model 3KR1. No longer made.
I would suggest the oil pump switch operate a relay instead of going directly to the electric pump as I doubt its contacts are intended for a lot of current.
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Old 09-06-2011, 08:35   #15
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Re: Electric Centrifugal Raw Water Pump 12V

Capn_Billl: Good points, thanks. Reliability is my #1 concern, but servicing of the engine-mounted raw water pump is a major pain due to its inaccessibility and trial-and-error method of belt adjustment; if a problem arises with it while I'm on a lee shore, I am toast. I could get a spare electric pump and have better reliability (I don't have the physical space for valves & tees to have dual permanently-installed pumps).

James: I would love to get rid of raw water via a keel cooler, and I did get a quote on Fernstrum KC (I did not get price for a Walter KC), but three issues keep me from doing this: 1) HIGH cost of keel cooler itself, 2) I have a transmission oil cooler that uses raw water, 3) I have a PSS shaft seal that has raw water injection.
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