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Old 13-05-2016, 19:36   #1
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Replacing impeller with electric pump

I have a Northern Lights genset that sits in a deck locker between the hulls of my catamaran. Its been recommended to me that a better method to ensure raw water flow to the engine is to remove the impeller and install an electric pump near the thruhull. Since the genset is well above the thruhull, the pump ensures good water flow and no problems with impeller blades getting into the heat exchanger.

Can anyone see any problem with this modification? The suggestion to do it comes from the local northern lights agent btw.

Thanks


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Old 13-05-2016, 20:30   #2
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Re: Replacing impeller with electric pump

It's expensive when done right with a submersible March pump normally used for A/C systems. Get the one in white and red epoxy housing, with magnetic drive.


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Old 13-05-2016, 20:37   #3
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Re: Replacing impeller with electric pump

I have a Westerbeke 12.5 and a Maspower 5.5 both with mag-drive electric pumps for raw water. I've been running the Westerbeke this way since 1999 and the Maspower since 2010. Both pumps have Groco strainers at the seacock and the pumps are mounted below the waterline. I have 3/4inch hose running directly to the heat exchangers. The rest out the raw water system is the same as the original pump set up. These are 110volt pumps wired directly to the 110 output of the gen (with an inline fuse).

Before all the haters start with their negativity, let me say this set up works much better than the crappy little Sherwood pump that each generator originally had. No more leaking seals, replacing impellers, etc. If these generators had decent raw water pumps with real seals (not little oil seals used as water seals) maybe my experience would be different. I keep a spare electric mag-drive pump but have never needed it. On the last summer Bahama trip, I probable ran over 100 hrs of 24/7 generators...no problem.

If your generator is above the water line, this is a great modification.
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Old 14-05-2016, 06:56   #4
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Re: Replacing impeller with electric pump

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Originally Posted by neworleansrich View Post
I have a Westerbeke 12.5 and a Maspower 5.5 both with mag-drive electric pumps for raw water. I've been running the Westerbeke this way since 1999 and the Maspower since 2010. Both pumps have Groco strainers at the seacock and the pumps are mounted below the waterline. I have 3/4inch hose running directly to the heat exchangers. The rest out the raw water system is the same as the original pump set up. These are 110volt pumps wired directly to the 110 output of the gen (with an inline fuse).

Before all the haters start with their negativity, let me say this set up works much better than the crappy little Sherwood pump that each generator originally had. No more leaking seals, replacing impellers, etc. If these generators had decent raw water pumps with real seals (not little oil seals used as water seals) maybe my experience would be different. I keep a spare electric mag-drive pump but have never needed it. On the last summer Bahama trip, I probable ran over 100 hrs of 24/7 generators...no problem.

If your generator is above the water line, this is a great modification.
I ment to say "over 1000 hrs"
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Old 14-05-2016, 07:06   #5
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Re: Replacing impeller with electric pump

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Originally Posted by neworleansrich View Post
.....................Before all the haters start with their negativity, .........
I was going to comment but I don't want to be labeled a "hater".
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Old 14-05-2016, 09:10   #6
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Re: Replacing impeller with electric pump

Quote:
Originally Posted by HKTim View Post
I have a Northern Lights genset that sits in a deck locker between the hulls of my catamaran. Its been recommended to me that a better method to ensure raw water flow to the engine is to remove the impeller and install an electric pump near the thruhull. Since the genset is well above the thruhull, the pump ensures good water flow and no problems with impeller blades getting into the heat exchanger.

Can anyone see any problem with this modification? The suggestion to do it comes from the local northern lights agent btw.

Thanks


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Our 10kw Panda has not had an impeller or drive belt for the water pump and alternator for 8+ years. [Both are available as tertiary back-up if needed.... read on...]

The March pump takes care of the gen raw water flow, and the house battery charger is on when the generator is running...

I also tied our raw water wash down pump into the raw inlet circuits for the engine and generator [properly done with Ts with valves] to act as back-up, to prime raw water circuits, and back-flush the raw water intake through-hull. Works great for all 3 purposes, but only as back-up in situations when it is inconvenient or dangerous to work on the malfunctioning system.

Don't hesitate to make changes that are for the better. The raw water pumps built on to our engines are not exactly engineering masterpieces... but they are money makers for impeller makers- not unlike printer ink...

Cheers!

Bill
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Old 14-05-2016, 09:18   #7
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Re: Replacing impeller with electric pump

It will work. It's actually done quite often. Unless you're having a problem with your current set up, I really don't see the need to spend the money.

If you choose to do it anyway, I'd love to sell you the pump.
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Old 14-05-2016, 09:25   #8
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Re: Replacing impeller with electric pump

I was once in a remote part of nova scotia and I ran out of impellors ( perkins peramaM30) I did have a couple of cheap rule baitwell pumps on board, Spliced one in the original line, turned in on and off manually. Got me home fine, but you would have to remember to turn it on and off. Pump was below the waterline so priming not an issue
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Old 14-05-2016, 13:49   #9
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Re: Replacing impeller with electric pump

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Originally Posted by rwidman View Post
I was going to comment but I don't want to be labeled a "hater".
Or worse still a "denier"

I have a 12V electric impeller pump supplying sea water into the mixing elbow on my main engine exhaust system. I installed this after I switched my cooling system over to keel cooling rather than re-plumb both the engine and the exhaust cooling. I use a relay powered by the oil pressure switch to ensure that the pump will not run with the engine shut down and flood back through the exhaust valves.

I have not had a lot of luck with in line centrifugal 12V pumps and the magnetically driven ones often don't supply much head.
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Old 14-05-2016, 14:18   #10
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Re: Replacing impeller with electric pump

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Or worse still a "denier"

I have a 12V electric impeller pump supplying sea water into the mixing elbow on my main engine exhaust system. I installed this after I switched my cooling system over to keel cooling rather than re-plumb both the engine and the exhaust cooling. I use a relay powered by the oil pressure switch to ensure that the pump will not run with the engine shut down and flood back through the exhaust valves.

I have not had a lot of luck with in line centrifugal 12V pumps and the magnetically driven ones often don't supply much head.
You mean lift? the March pumps do 19' head but must be below waterline to work optimally in my experience.
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Old 15-05-2016, 02:01   #11
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Re: Replacing impeller with electric pump

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You mean lift? the March pumps do 19' head but must be below waterline to work optimally in my experience.
Centrifugals will drain back unless some sort of foot valve is fitted and will not self prime so yes they should be installed with positive suction head.

19' of head is about 8psi of output pressure which is not much but the impeller pumps probably don't put out much more than this anyway, if at all.

I think the advantage of the impeller pumps is probably that to a degree they are positive displacement and will pump a fixed volume at each rpm.

Zillions of engines are fitted with centrifugal pumps and if a reliable one can be found and can be fitted below the waterline there appears to be no reason this solution would not work.
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Old 16-05-2016, 14:40   #12
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Re: Replacing impeller with electric pump

I have 3 A/C systems and a 6 KW Kohler for which i use the same model March (or Calpump) centrifugal pump on each one. No problems in more than 15 years of operation. Genset pump only runs when genset is running.
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Old 16-05-2016, 15:40   #13
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Re: Replacing impeller with electric pump

I just got through doing this after my raw water pumps seal failed without my knowledge and sprayed my generator with salt water for some indeterminable time, I only found out after it eventually seized.
My Nexgen requires 4 GPM of water flow, the March pump I used if I remember the specs flows 8 GPM at 10' of head. I was concerned this would be too much and I would have to reduce it down, but I didn't. It is obviously more flow, but the generator handles it easily.
Wired directly into the AC output of the generator, pump doesn't run without the generator running so that part is fail safe.
As other have indicated the March pumps must be below water line, they will not prime.
March pump and new mechanical water pump were about the same price, March pump has no impellers to fail and clog the heat exchanger, and based on my experience with them on air conditioners, they run longer than my generator will most likely last before failure. Think about it, how many years have you seen them run AC's on a boat in the Marina?

I see no downside to this, and makes me wonder why generators don't come this way? I guess it's another thing to wire and install where a manual pump isn't?


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