Some Fun Saturday Reading. If You Own One of These, This Is The Story of The Year For You.

The Jabsco 4840 Pump in all it's glory. It aint no Raquel Welch, but at least you can mess with it.
Here it is, what you all have been waiting for…or not.. How to rebuild a Jabsco 4840 Pump… oh you say.. I needed that, well, this is no ordinary guide to rebuild a pump its a special one for Rebuilding the Jabsco 4840 Water Pump for CM-300 Cadillac Crusader.. To be specific. Thanks to fellow WoodyBoater Garret Spears for saving the day… for at least 2 of you.. All kidding aside, if you own one of these suckers, this is a life saver.. Book mark it and carry it with you every place just in case you need it. And a 5 gallon bucket….

Rebuilding the Jabsco 4840 Water Pump for CM-300 Cadillac Crusader. By Garret Spears

The Jabsco 4840 pump in all likelihood was designed and built just for Cadillac Crusader engines. In talking with Keith Evans who was with Jabsco just after they moved from Burbank to Costa Mesa California the conversation indicated that drawings and other documentation used in engineering was paper and if still existent is somewhere in archived filing. As a result I decided to document this painful rebuild.
Jabsco, founded in 1938, went from an independent small company to being owned by ITT. In 201,1 after the breakup of ITT into three separate companies, Jabsco ended up as a subsidiary of Xyleminc, one of the three separate companies formed out of the ITT breakup. Xyleminc can be found as Jabsco invented and patented the rubber impellor pump in 1940.
In searching for the 4840 pump I found the Jabsco pump 14210-0001. This pump was identified by as internally the same pump and that part numbers for seals and bearings could be used from it. In looking at the drawing for this pump it appears to be true for rebuilding of the 4840 but there are several miss-leading items. The shaft bearing is correct as listed as a Jabsco part number 92600-0060. The bearing seal, 913-0000, is correct but it has to go in a different location and the primary pump cavity seal, 96080-0080, is correct but a significant departure from the structure of the original primary pump cavity seal but does the job. Their drawing does not show two other seals found in the 4840, one a slinger washer and a fourth seal a secondary pump cavity seal.

Cross Section of 4840 Pump

The bearing is an angular contact ball bearing, double row, with metal shields on both sides. It is a SKF brand with part number of 3204 A2ZTN9/MT33. An alternative bearing is the 3204 2RS1TN9/MT33 having rubber seals instead of metal shields. The seals or shields are to keep out foreign particulate materials from the races and lubricant in the bearing. The rubber sealed bearing, if selected, is an additional drag on driving the pump shaft. The bearing is pressed into the pump body and retained by a lip in the pump body. A snap-ring is installed after the bearing is installed to lock the bearing in place. The snap-ring side of the pump is exposed to the environment through the mounting hole on the front bell housing of the engine. The other side of the bearing in the original assembly was shielded from the environment by a rotary shaft seal made of rubber material with no metal shell that easily disintegrates when taking the pump apart after more than forty years of service.
The pump body has two slotted openings to the environment between the bearing and the water pump cavity. This environment in the boat is a foot or so above the bottom of the bilge. The pump is mounted on the bell housing covering the flywheel end of the engine. The face of the pump going to the bell housing has the bearing exposed to the environment through the hole that the shaft for driving the pump is inserted into on the bell housing. The real threat to the bearing comes from the water being pumped through the pump cavity either due to leaks past or failure of the primary and secondary seals.
In the original design of the pump the engineering done to prevent any water getting to the bearing consisted of the bearing seal, a slinger washer, a secondary lip seal installed from the bearing end of the pump going to and facing the pump cavity and a primary lip seal installed from the pump cavity side. In all there are four seals between the bearing and the pump cavity to protect the bearing.
The primary and secondary lip seals facing the pump cavity are easily obtainable since the bore or outer diameter of the seal and the inner diameter are standard dimensions for each. The original primary seal installed from the pump cavity side has a bronze or brass shell fully enclosing it which is not a standard rotary seal. The part number marked on it is 11120-Q6 and the symbol C/R for Chicago Rawhide. This seal is obsolete and has been replaced by the part number CR6903 from SKF/Chicago Rawhide.
The replacement for the primary seal can be a single lip seal of type A but a double lip would be nice in order to get out of using the secondary seal mentioned above. Double lip seals are not available unless quite a few are ordered. The second feature of any of these seals is that they are made from Viton or Nitrile polymers to be compatible with water. These two seals can be found through SKF/Chicago Rawhide or Daemar Inc.
The primary pump seal can be either the Jabsco 96080-0080 or one of the following Daemar part number S06212525A, shaft dia, 0.6250 in Bore dia. 1.2500 in, width 0.252. The SKF/Chicago Rawhide part number is CR6903, same dimensions.

Type A Seal Encased in Nitrile Cross Section
The secondary lip seal not identified by Jabsco installed from the bearing end of the pump, has a bore diameter of 1.000 inches and seats against the bottom of the primary seal. The Daemar part number is S06210025A, shaft dia. 0.6250 in. Bore dia. 1.0000 in. width 0.252. The SKF/Chicago Rawhide equivalent is CR6143, same dimensions. This seal effectively creates a double lip seal in conjunction with the primary seal.

The bearing seal turns out to be a mystery. Originally, when taking apart my pump, it was below the annular ring that retained the bearing. It was also installed using something akin to Glyptol. It needs to have an inner diameter of 0.937 and an outer bore diameter of 1.625. A simple Type A lip seal will work but finding one that matches up to these dimensions has not been realized. The inner diameter corresponds to enlarged pump drive shaft section and the outer diameter of the slinger washer mounted on the shaft. This seal would ride on the shaft and partially on the slinger washer. A SKF/Chicago Rawhide equivalent part would be CR9307 but has a smaller bore diameter.
The JA 913-0000 will install in the annular ring just below the bearing as shown in the Jabsco pump14210-0001. This ring has a bore of 1.700 inches allowing for easy installation of the JA 92700-0000. In my pump there was nothing in this annular ring. The diameter of the shaft varies from 0.934 to 0.937 inches where this seal will be. In searching for an equivalent seal to the JA 913-0000 none was found. The seal is by NTK and is marked “5965 SC 171 093 17 3” indicating 0.171 bore, 0.937 ID and 0.170 width. NTK stands for Tsuang Hine Oil Seal Corp in Taiwan. The 5965 is probably their part number. I have found no equivalent.
The original bearing seal had its lip facing the bearing as it came out of the pump. There was no evidence of lubricant in the the bearing and this seal. Because the drive shaft for the pump is a little undersized where any of the original seals occur there might have been an expectation of water leaking past the seals and lubricating all the lips. Until a drawing is found showing the dimensions on this shaft the assumption has to be the measured dimensions reflect some wear on the shaft. Lubricant should have been used generously on all the seals except the slinger.
Going with no bearing seal should not be a major problem as there three seals between the bearing and the pump cavity plus the bearing has built in shields. On the pump drive shaft going from the bearing to the pump cavity there is a slinger washer of black rubber between the bearing and the secondary and primary seals. As the shaft revolves any water leaking past the secondary and primary seals should hit this slinger and be ejected through the openings on the side of the pump where the slinger washer is located. This washer is referred to as a “slinger seal”.
Should be ejected is the key phrase. The slinger seal is a simple washer without vanes and water adhesion to it versus any other surface type like metal should be greater resulting in centripetal ejection and keeping the face of the bearing free from water. This is a pretty standard approach to protection. Jabsco does not have this seal and getting one has not been possible unless custom ordered. Use the original one if possible.
The best recommendation is to use the JA 913-0000 to protect the bearing. Use lubricant generously between the bearing and the seal.
All of these seals should be installed with excess lubricant, such as used in water pumps. The lips need lubrication. The JA 913-0000, bearing seal, should be installed with the lip facing the bearing to retain lubricant on the bearing side; all others should be with lip facing the pump cavity. All seals can be installed without usage of a press or special tools.
To get the bearing onto the shaft lubricate well and use a long socket that covers only the inner race and a 5 pound blacksmith hammer. It is a very tight fit.
The primary and secondary seals can be installed by using finger pressure. Lubricate bores and seals then pus in the primary. If there is any mis-alignment with the bore it will not go in. The secondary behaves the same way and the primary can be pushed out so use a finger to push the secondary and the another to tell when the primary starts to move. The bearing seal is has a bore that is closer to optimum and using a screw driver and working around the seal it can be seated.
By heating the pump body where the bearing fits thermal expansion will allow for a slide in fit. A drift on the outer race or a socket that hits the race and easily fits the bearing bore can be used to get the bearing in below the keeper ring grove. Iused a brass drift and alternated back and forth across the race.

Now, just in case you need more info, and who wouldn’t?  Here is Garret’s email – and garret has kindly included a shopping list.. Thanks Garret.
Items ordered from Fisheries Supply in Seattle:
JA 3298-0000 pump cavity gasket
JA 1210-001 Impellors (2 required)
JA 18713-0000 Keeper ring that goes on shaft against bearing
JA 92600-0060 Bearing
JA 913-0000 Bearing Seal
JA 92700-0060 Primary pump cavity seal Distributor for SKF and timing belts. A branch in Seattle.

6 replies
  1. chad
    chad says:

    You have NO idea how long I’ve waited to learn how to rebuild a Jabsco 4840 Pump. Thank you Jesus (and Garret) for answering my prayers!

  2. Rick
    Rick says:

    I’m more than ready for Douple Jepordy now!
    Alex the answer is “How do you rebuild a Jabsco 4840 Pump?”

  3. Al Benton
    Al Benton says:

    There was a 21′ Capri sitting in the “Field of Dreams” at the Sunnyland Boat Show back in ’08 that had a rare Jabsco 4840 Water Pump in it. The price was right, I could have picked it up for a “song and a dance” at the time. I could kick myself around the block for not trying to put a number together to obtain that pump but it’s all Mom’s fault. I never learned to sing OR dance. Dang!!!

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