So far torn down and repaired 3 bilge pumps, 2000 Rule, 3700 Rule and 2000 China pump

Here is the last one I fixed, a Rule 2000. The rubber seals failed, they wore out and let in bilge water. Cleaned it and painted the inside too.
Hardest thing was prying off the impeller. it actually broke as it was crevice corroded to the motor shaft. But some Devcon epoxy repaired it. It is a looser fit on the shaft now, and I packed it with the grease. Put in new brushes which I had to sand to fit.
https://photos.app.goo.gl/oeBsabs7vszh1e3P8

The seals are not a problem to get, the number to use is 350364, and they fit perfectly packed with dielectric silicone grease. I used 2 seals like the OEM setup.
Rock Auto had the best price for the seals

Amazon for the waterproof grease
Amazon.com: Dielectric Silicone Grease - Waterproof and Non-Conductive Lubricant for Electrical and Automotive Applications - Easy Application 4oz Brush Top Can : Automotive

Amazon for the brushes
20PCS J471 Carbon Motor Brushes, Replacement Brush DC Solar Energy Deep Well Brushes, for Pump - - Amazon.com

The bushing grease I used 30 wt synthetic motor oil, and greased the bushing and shaft with moly grease from O'Reilly. I poured some oil into the bushing area. There is a felt pad that soaks up oil and is meant to release it slowly to the bronze bushing. But you know when you wash the pump out, it will get wet. And take a long time to dry if ever. So for the lower bushing I ground off the rivets and cleaned the felt pad and let it dry. I then used a copper wire through both holes to hold the bushing and spring and plate on the end cover. I figured a high moly grease a good idea.
Mystik 14 Ounce Hi-Temp Moly Grease 665056002080 | O'Reilly Auto Parts (oreillyauto.com)

 

The Rule 3700 had failed as bilge water got inside. The pump housing cracked on top. Used Loctite marine epoxy.
And I repaired a brush lead. I notice the negative leads get destroyed in wet pump motors.
Rule 3700 uses one sealed ball bearing for the lower bearing. 608-2rs
https://photos.app.goo.gl/SPaLjjXDiAuewbiN9

 

China 2000 bilge pump from Amazon is actually a decent pump. It too failed as the shaft rusted at the rubber shaft seal, let in water. the rubber seal itself was not worn out.
NovelBee 12V 2000 GPH Boat Marine Electric Submersible Bilge Pump with Hose ID 29mm (amazon.com)

It is actually a superior pump as it uses real sealed ball bearings upper and lower, not bushings. The bearings are 608-2RS, very common. It's weakness is the shaft rust where it fits the seal and them it leaks in water. Critical issue is use the right waterproof grease, it lasted just 2 years, I paid $30.
10 Pack 608-2RS Ball Bearing - Double Rubber Sealed Miniature Deep Groove Ball Bearings for Skateboards, Inline Skates, Scooters (8mm x 22mm x 7mm),Green: Amazon.com: Industrial & Scientific
The impeller is also held on by a SS circlip, makes it easy to get off.
Not as many photos.
https://photos.app.goo.gl/EW9cjyKe3i9VJwDWA

The seal grease I used dielectric silicone waterproof grease. It is critical to use such a grease as it repels water. The electric pump wires also get greased, it seals them and allows them to slide on the oval rubber bushing

The fixed Rule 3700 and Chinese pump have been in the boat for a while now and working fine.
I was surprised the Rule 2000 SS motor shaft is made from a SS that can rust.... First time I have seen that on a Rule pump, but it was an old pump from many years ago.
The Rule 3700 is a newer pump I bought in the last 5 years, and it had no rust. BUT, the motor housing inner plastic is strong and brittle. It got dropped in shipping and cracked and the seller sent me a new one. I had fixed it sort of, but this past winter it leaked and let water in after being in the bilge a few years. This time it is fixed better.

 

Regarding the electric wire black rubber oval bushing, do not remove it from the motor housing, just grease the wires with the silicone grease and slide them in or out.

 

How did you repair the pitted shaft on the Chinese pump? I wonder if armature assemblies are being sold?