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Old 04-08-2020, 12:10 PM   #21
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I've upgraded the original Sherwood seawater pump on our Cummins 6BTA 5.9 M3 to a Seaboard Marine SMX 1730 pump. Replaced the impeller every two years and 1600 hours. So far (two replacements) it has always looked OK. Thinking I might go to annually.
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Old 04-08-2020, 12:11 PM   #22
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Quote:
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I did that recently based on Ted's photo. Full project writeup here: Raw Water Impeller Strainer
Excellent post! Thanks!!!
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Old 04-08-2020, 12:59 PM   #23
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Mr Insequent,
This was my post on the thread you referenced:

Aboard Salty, I have spare RW pumps for each JD main and the generator. I rebuild the pumps (new seals and gaskets) as soon as I swap them out, and store them with a new impeller ready to install. I can swap out the entire pump as quickly as installing an impeller in situ. Also, the new seals only cost a couple bucks, and are cheap insurance against the inevitable.

We boat year round down here, so I usually swap out the pumps at 2 years.

I use plain, fresh stock impellers...never saw the need for the high$$ impellers.
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Old 04-08-2020, 03:22 PM   #24
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Changed my impeller yesterday. I also have the Cummins 6BTA 330 hp and changed over to the SMX 1730 pump a few years ago. Nice pump, definitely better built compared to the Sherwood (stock one). The old impeller had 2 years of use, and almost 500 hours on it. On close examination, the old impeller looked "almost new".

During the winter, I don't use the boat. I store the engine with a mixture of freshwater and "salt away" in the raw water system. The local dock water is shut off to prevent freezing, so if I want to keep the saltwater out of my system, no running of the engine during the winter down time. So, I "bump" the starter every month to move the impeller to prevent it taking a set. This seems to be working??
I think I probably could go 3 years if I removed the pump cover annually to visually inspect the impeller condition. However, being somewhat conservative, I think I will do the annual inspection and stick to the 2 year interval.
Richard C., how long do you think (hours) before the pump might need a rebuild or are you going to wait for a visual signal (like a leak)?
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Old 04-08-2020, 03:35 PM   #25
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I replace our impellers annually at the start of the season. At $22 each, and an easy job, its a no brainer for me.

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Old 04-09-2020, 01:01 AM   #26
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Geez Ken,
My one impeller (basically same price for SMX brand or Sherwood equivalent) cost over $100!!
I know, not that bad on the scale of boat costs
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Old 04-09-2020, 06:51 AM   #27
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Even well maintained impellers can fail with out warning and dump chunks of impeller in the system.

The only cure I know of is a Y strainer of the right size to collect the chunks etc after the pump..

Not very expensive , and if there is a cooling problem its only a few seconds to check the mesh basket rather than anything else.
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Old 04-09-2020, 09:33 AM   #28
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Good points FF. Ted has suggested the strainer as well. Even though it adds another potential leak point (2 hose clamps and the strainer basket itself), if you have the room for it, the strainer does make sense should you suffer any kind of impeller damage.
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Old 04-09-2020, 10:20 AM   #29
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Quote:
Originally Posted by FF View Post
Even well maintained impellers can fail with out warning and dump chunks of impeller in the system.

The only cure I know of is a Y strainer of the right size to collect the chunks etc after the pump..

Not very expensive , and if there is a cooling problem its only a few seconds to check the mesh basket rather than anything else.
Or.... on the newer popular Cummins models that end in "A", the A stand for "aftercooler"....and that is where you will find the pieces of impeller as they can't get past there.
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Old 04-09-2020, 12:24 PM   #30
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True Baker, true.
But, disassembling the aftercooler (which really should be pressure tested when disassembled), or removing the hose and "fishing out" the small pieces through the opening, sounds like much more work than just opening a strainer and removing the bits. Now having the space to place a strainer between the raw water pump and the aftercooler can prove difficult, especially if on the Cummins 6BTA with an installed fuel cooler between the pump and aftercooler. I removed my fuel cooler and now there is probably room, so I am considering it, although so far, there has not been an impeller issue. Only takes once though.
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Old 04-09-2020, 01:52 PM   #31
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I see coolant filters mentioned. What kind or brand for an inline filter?
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Old 04-09-2020, 01:59 PM   #32
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True Baker, true.
But, disassembling the aftercooler (which really should be pressure tested when disassembled), or removing the hose and "fishing out" the small pieces through the opening, sounds like much more work than just opening a strainer and removing the bits. Now having the space to place a strainer between the raw water pump and the aftercooler can prove difficult, especially if on the Cummins 6BTA with an installed fuel cooler between the pump and aftercooler. I removed my fuel cooler and now there is probably room, so I am considering it, although so far, there has not been an impeller issue. Only takes once though.
Man I thought I typed out a reply to this...maybe I replied improperly on some other thread.

No disassembly required to find pieces near the aftercooler. The raw water goes straight into the bottom from the fuel cooler(or your bypass hose) and run into a dead end right there. They would be in the lower end cap of the cooler. Just pull the hose from the fuel cooler to the aftercooler and they would be right there.
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Old 04-09-2020, 06:16 PM   #33
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Quote:
Originally Posted by firehoser75 View Post
Changed my impeller yesterday. I also have the Cummins 6BTA 330 hp and changed over to the SMX 1730 pump a few years ago. Nice pump, definitely better built compared to the Sherwood (stock one). The old impeller had 2 years of use, and almost 500 hours on it. On close examination, the old impeller looked "almost new".

During the winter, I don't use the boat. I store the engine with a mixture of freshwater and "salt away" in the raw water system. The local dock water is shut off to prevent freezing, so if I want to keep the saltwater out of my system, no running of the engine during the winter down time. So, I "bump" the starter every month to move the impeller to prevent it taking a set. This seems to be working??
I think I probably could go 3 years if I removed the pump cover annually to visually inspect the impeller condition. However, being somewhat conservative, I think I will do the annual inspection and stick to the 2 year interval.
Richard C., how long do you think (hours) before the pump might need a rebuild or are you going to wait for a visual signal (like a leak)?
Hi Tom,

I don't have a clue how long the SMX will last, but I sure am impressed with how long the impellers last. When I open up to change impellers I feel around inside, and take a peek at the cam. Silicone grease everywhere when installing new. 3,100 hours and so far seems perfect.

On my Volvo 44, the less robust Johnson pump lasted 4500 hours before replacement. I rebuilt once with new seals before that. It showed it needed that by leaking near the seals. Impellers sometimes did not last a summer (400 hours), even though I removed for the winter and installed a new one in the spring every year. Impeller cover plates lasted maybe 1200 hours before wear grooves got too big.
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Old 04-13-2020, 01:00 PM   #34
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My Cummins SMX gets a new impeller annually, new seals every 3 years.
The spare I carry is new, not the one I took out last year.
I’d rather do it on a scheduled basis than as a surprise.
Mr Murphy says that if the impeller or seals fail, it will be at the worst possible time, so with a single engine, I just won’t risk that.
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Old 04-13-2020, 01:07 PM   #35
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As a note on impeller failures and when they happen, it seems like impellers (engine or generator) almost always fail on startup. I've only seen a single failure once the system was already pumping, and that impeller was quite old when it failed. The only other times I've seen loss of raw water flow on a running engine, it's been due to sucking up trash that clogged the intake thru hull.
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Old 04-13-2020, 01:08 PM   #36
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Last year we did about 450hrs. We change them once a year.
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Old 04-13-2020, 02:48 PM   #37
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Great discussion

Lady Sue, 1982 Mainship I, original Perkins, has been getting a new impeller annually since 1990.
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Old 04-13-2020, 06:10 PM   #38
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Every two years which is about 200 hours. They don't cost that much and it's a lot easier making the change at the dock.
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Old 04-13-2020, 09:55 PM   #39
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Quote:
Originally Posted by RCook View Post
I've upgraded the original Sherwood seawater pump on our Cummins 6BTA 5.9 M3 to a Seaboard Marine SMX 1730 pump. Replaced the impeller every two years and 1600 hours. So far (two replacements) it has always looked OK. Thinking I might go to annually.
We did the same upgrade to the SMX., and cary the Sherwood as a spare. We are trying a Staycool impeller in the SMX pump. So far so good (400+hours)
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Old 04-13-2020, 11:08 PM   #40
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My impeller kits are $75. I carry two as spares. I also carry two complete pumps as spares. One is new, the other was rebuilt by the dealer.
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