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Old 06-24-2021, 07:38 AM   #1
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Changing an impeller advice

I want to change the raw water cooling impeller on a new to us Grand Banks 36 with a Cat 3208NA 210 HP engine. The available space is very tight. I'm thinking it may be necessary to temporarily remove the water pump to make the change. Does anyone have experience with this set-up and what's the best approach to use? Thanks.
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Old 06-24-2021, 07:56 AM   #2
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just replaced mine on a 3304 not sure if its similar to yours.

I purchased the large impeller puller and had to modify the center threaded Shraft by shortening it about 2 inches. that worked for me.

in general impellers always seems to be in hard to reach places and sometimes the raw water pump have to be removed.
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Old 06-24-2021, 08:03 AM   #3
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Look at impellertool.com. They make a funnel type of tool that makes it very easy to reinstall the new impeller. The starboard engine on our last boat was almost impossible to change the impeller on. The mechanics that had serviced the boat said they had to pull the pump to change the impeller. With the tool I was able to change the impeller in under a half hour with the pump in place. I bought a Jabsco impeller puller. Had to get some metric threaded rod and put double nuts on it to pull the old impeller since the T handle that came with the pump wouldnít turn, the T hit a pipe. No affiliation.
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Old 06-24-2021, 08:47 AM   #4
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I've read it's not uncommon to remove the pump, swap in a spare pump right away, and then change the impeller in the "now removed" pump on the bench.

BTW, that impeller tool mentioned above is the greatest thing since sliced bread.

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Old 06-24-2021, 08:50 AM   #5
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Quote:
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I want to change the raw water cooling impeller on a new to us Grand Banks 36 with a Cat 3208NA 210 HP engine. The available space is very tight. I'm thinking it may be necessary to temporarily remove the water pump to make the change. Does anyone have experience with this set-up and what's the best approach to use? Thanks.
I am due soon for my 1st impeller change on the raw water pumps on 3208NAs. As far as I can tell there isn't enough clearance without pulling the pump.
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Old 06-24-2021, 10:16 AM   #6
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Hi NedZ,

Unfortunately, one of the unadvertised "features" of the CAT 3208 in marine service is the virtual reality of having to remove the raw water pump from the engine to replace the impeller. With all due respect to CAT, your design guys need to pay more attention to post-installation service needs of an engine in your basic marinization design(s). And that's a polite way to say "you guys stink".

So yes, remove the pump, haul it ashore onto your workbench, obtain any of the plethora of tools needed to remove and reinstall your impeller (and service your pump in general), and have at it. Then plan to do so again after your chosen service interval (I chose 300 hours for my comfort level), then rinse and repeat.

And given the silly thing is belt-driven, watch the tension, alignment, and service life of the drive belt like a hawk. Personally, I routinely replaced my pump belt at the same time as the impeller, whether it needed it or not. Losing a belt underway leads to a rapid overheat, just as losing an impeller. And that's not a good thing, for so very many reasons.

Regards,

Pete
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Old 06-24-2021, 12:32 PM   #7
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Thanks for the input

Thanks all of you. I'm afraid I will need to remove the pump as you suggest. I do have a Jabsco impeller puller. Now just need to deal with the hose connections and pull it. I may swear a little!
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Old 06-24-2021, 12:53 PM   #8
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On my 3208T 320hp Cats, my Starboard engine was no problem, but my port engine had limited access so I would just pull the whole pump.

The boat was up north, so winterization just involved pulling both pumps and taking them home. I would pull the impellers, inspect, and if good replace every other year. Then reinstall at spring commissioning.
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Old 06-24-2021, 02:42 PM   #9
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Originally Posted by ranger42c View Post
I've read it's not uncommon to remove the pump, swap in a spare pump right away, and then change the impeller in the "now removed" pump on the bench.

BTW, that impeller tool mentioned above is the greatest thing since sliced bread.

-Chris
That's what I've done for years, not only does it simplify the job and make it go more quickly you also always have a spare pump. I obviously also carry spare impellers. Another little trick is replacing the screws on the cover with studs and nylock nuts.
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Old 06-24-2021, 02:58 PM   #10
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Originally Posted by jungpeter View Post
Hi NedZ,

Unfortunately, one of the unadvertised "features" of the CAT 3208 in marine service is the virtual reality of having to remove the raw water pump from the engine to replace the impeller. With all due respect to CAT, your design guys need to pay more attention to post-installation service needs of an engine in your basic marinization design(s). And that's a polite way to say "you guys stink".

So yes, remove the pump, haul it ashore onto your workbench, obtain any of the plethora of tools needed to remove and reinstall your impeller (and service your pump in general), and have at it. Then plan to do so again after your chosen service interval (I chose 300 hours for my comfort level), then rinse and repeat.

And given the silly thing is belt-driven, watch the tension, alignment, and service life of the drive belt like a hawk. Personally, I routinely replaced my pump belt at the same time as the impeller, whether it needed it or not. Losing a belt underway leads to a rapid overheat, just as losing an impeller. And that's not a good thing, for so very many reasons.

Regards,

Pete
Jung even with the "Impellertool" you still need to remove the pumps?
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Old 06-24-2021, 03:32 PM   #11
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We remove the pump on our 855 Cummins, belt driven so an easy job.

Pump is big enough that no special tools are needed for the impeller
10 minutes on table in cockpit

We carry a spare pump, impeller removed so as not to set.
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Old 06-24-2021, 05:42 PM   #12
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Jung even with the "Impellertool" you still need to remove the pumps?
Well, I can only state that on my 78-vintage 3208NAs, there is an external cooling line and fittings (for the oil cooler, as I recall) that precludes removal of the pump cover and impeller in situ. Hence, off come the pump(s) to replace the impeller. Not too tough on the starboard engine of a twin engine installation, as the coolant pump is inboard. A royal PIA on the port side.

Once off the engine, various "Impellertools" will aid and abet the impeller change, as well as service to the rest of the pump as required.

Regards,

Pete
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Old 06-24-2021, 06:00 PM   #13
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You guys must have some ridiculously tight applications. I have 3208’s, it is 3 bolts and the bracket is then loose from the engine. Remove the belt, loosen two hose clamps and spin the pump around. Four screws and off comes the back plate. Two screw drivers and you pop the old impeller out.. If some one installed the correct impeller there is a cheap tool to remove the impeller but I have never had an issue with just popping the impeller out.

Even it you want to do it on the bench there isn’t much to taking the pump off the engine.
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Old 06-24-2021, 09:02 PM   #14
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Would some enterprising younger fellow please start to remanufacture the 'Speedseal Run Dry' impeller kits ?
Sheesh if I could turn the clock back I'd jump at the opportunity. It would make a nice family enterprise for a someone with an engineering background.
There's also a large market with the military as well as us guys.
I had one fitted to a Birchwood/Perkins engine for over 10 years with no need to change the impeller.
I have one fitted to my present boat for over 8 yrs which has done thousands of miles and never had to change an impeller.
The man who designed it had to give up the business for health reasons.
C'mon you guys there must be someone out there who'd like a business handed on a plate.
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Old 06-24-2021, 09:59 PM   #15
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Would some enterprising younger fellow please start to remanufacture the 'Speedseal Run Dry' impeller kits ?
What's so good or special about them?
How do they make impellers last so long?
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Old 06-24-2021, 10:21 PM   #16
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OK Simi. Brief description.
Firstly the reason impellers burn out is lack of water (to lubricate) so they overheat and burn out/disintegrate.
The idea of the 'Run Dry' is to allow them to spin dry for up to 20 minutes as there's no friction on the inner/outer parts of the impeller they don't overheat.
The existing Jabsco body is kept, after removing the old impeller a ptfe insert is placed then a new impeller is inserted, the old outer cover and screws are discarded. The old 6 tiny slotted screws are replaced with 4 bolts with a large knurled nut (no tools are needed to fit/replace them).
The outer cover is bronze but slightly thicker than the original and retained by 4 knurled nut headed bolts, inside the outer cover/face plate is a brass disc which can freely rotate, an 'O' ring seals the face plate.
Knurled nuts, 'O' rings, ptfe sheet can all be bought freely on the open market as can the impellers, the only part which requires machining is the face plate.
Living on a boat has its freedoms but also its restrictions, if I lived in a house I'd put a lathe in my garage and make them myself.
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Old 06-24-2021, 10:40 PM   #17
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Changing an impeller advice

Ned,

I have twin 3208NA engines in my boat and change the impellers without taking the pumps off the engine. Is it tight? Yes, a bit, but doable.

I take off the rear cover, being careful not to lose the small bolts that hold on the cover. I then use a pair of pliers to grab the impeller by the vanes. I pull on one of the vanes then move across to the vane opposite the first one I pulled and pull it. After doing this a few times, the impeller starts to pull out.

Once out, I take the new impeller and lube it up with the glycerin that comes with it or with dish soap. Iíve tried several different things that others have suggested including collapsing the impeller with zip ties or other clamps, but, to be honest, I found it easier just to squeeze the impeller down and start to push it into the housing while twisting. Once the splines engage, this is where it becomes a bit difficult but, again, still doable.

I use a rag or other cushion to cover the exhaust manifold and, placing the back of my hand against the exhaust manifold, I push the impeller into the pump body with my palm. It sometimes helps to use the fingers from your other hand to collapse the vanes a bit.

Once you do the first one and figure out the leverage points, the subsequent one is easier.

For me, the starboard engine is easy as the pump is accessible in the midline of the engine room. The port engine requires a bit of contorting as the pump is near the side of the hall but itís still accessible.

I suppose the worst that could happen is you are unable to get the impeller back in and have to take the pump off. Might still be worth a try.

Let me know if you have any other questions.

Matt
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Old 06-25-2021, 03:11 PM   #18
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OK Simi. Brief description.
Thanks for that.
Cruising full time our seacock is always open so I expect lack of water will not be a problem for us.

I did know about the wing nut quick release and that's an easy mod but the machined disc inside was a new one.
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Old 06-25-2021, 08:17 PM   #19
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Simi, the idea is that if your raw water strainer gets blocked you will have no water to cool the impeller.
The system used knurled nuts not wingnuts.
The ptfe insert and machined disc are the key factor in keeping the impeller cool, the retaining nuts are for quick impeller changes.
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Old 06-28-2021, 06:18 AM   #20
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"Now just need to deal with the hose connections and pull it."

There is a special tool to make removing a hose from a fitting easily.

https://www.jbtools.com/sg-tool-aid-...SABEgKog_D_BwE
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