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Old 21-11-2011, 20:24   #1
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Alternative to Seawater Impeller Pump ?

Can anyone here see a problem with replacing the engine-driven impeller sea-water pump with some alternative, such as electric drive?
What kind of pump would you recommend, if you were to do this?
My Volvo MD17 has a double, piggy-back Johnson pump, engine driven. The inner unit pumps antifreeze through the engine and keel cooler. The outer unit only pumps fresh water into the exhaust elbow. You have to remove the outer pump and shaft to get at the engine cooling pump impeller - more than a bit awkward! It appears that the shaft and inner seals need replacing, again. I was thinking of putting the original Johnson F4B-9 single pump back on the engine for engine cooling, and using a separate little pump to squirt water into the exhaust elbow. Both pumps would then be easier to maintain.
Sound reasonable? - if so, what kind of pump would you recommend for getting water to the exhaust elbow?
(Yes, I have searched the CF forums, to no avail - enter sea-water pump in the search field, and you get thousands of completely non-related threads, including one from SSSSM !)
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Old 21-11-2011, 20:30   #2
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Re: alternative to sea-water impeller pump?

i have run my 3cyl genset for many years using a 12v bait well pump 12 gph.
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Old 21-11-2011, 20:37   #3
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Re: alternative to sea-water impeller pump?

Not a bad idea actually. Many modern diesels require the 12 volt DC systems to be functioning for them to run. This wasn't the case so much with diesels not too long ago which did not need any electricity to operate. To start, obviously yes for larger diesels.

You would want a positive displacement pump of some sort which could pull water uphill in order to get it primed.

I know how expensive some raw water engine pumps are.
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Old 22-11-2011, 08:16   #4
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Re: Alternative to Seawater Impeller Pump ?

I can easily place a pump at or below W/L, so it doesn't really have to be self-priming. I will check the specs with Johnson Pumps to get an idea of the capacity needed in the pump.
Probably also a good idea to put a flow meter in there so I get a warning if the beast stops pumping.
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Old 22-11-2011, 12:32   #5
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Re: Alternative to Seawater Impeller Pump ?

You will want a positive displacemnt pump not only for priming but also to make sure you overcome exhaust and muffler pressures.
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