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What is the motor and what is the pump?
Lingo can be confusing. Actually the "motor" only refers to the part that makes the "pump" turn. It's the electronic part of the two. Typically the motor is called a "motor" and the pump is called the "wet end". The pump and motor together is called the pump/motor complete. Sort of obvious when you think of it.

How Important is matching the pump and motor?
Think of it like putting a small engine in a big car. It might last but not long. OR, a big engine in a small car. Wasted power. So engineers match the pump with the motor. Too often a person will think themselves cleaver putting a larger impeller on a pump and thinking they are getting more power for a cheaper price. Again, you can put a small engine in a car and pull a trailer with it thinking those guys with a truck and big engine are losers. They are not and you will be.

What is a frame?
Motors are made to match with a certain design pump. Usually a pump for one frame will not match a motor of another. Some manufacturers have made pumps that match a multiple frames. There is also an aligning issue. Be careful you get a matched frame. Older White Pumps have special order motors to match that frame. J-Pumps are all the same 48 frame. J "series" after 2002 used the 48 frame early in production, changed to a 48b in 2009, and many are the 56 frame.
Measurement between 2 post is 3 5/8" for 48 frame; 4 1/8" for 56 frame.

What maintenance should I do on a pump?
Usually none. But watch for leaking pump/wetend. Unless freezing damaged, the most common leaking of a wetend is the seal. Pumps come with different size/style seals so you need to match the correct size. Also the type of seal is becoming popular. The "ozone" seals are more resistant to leaking than a standard seal. Leaking seals can easily damage your motor.

How do I separate the pump from the motor? The pump attaches to the motor in two basic areas. First, 4 long bolts go through the motor and attach to the pump and hold the complete pump to the motor. Loosen but do NOT remove bolts. They also hold the motor together. Just disengage bolts from the pump.

Next and last is the motor shaft screws into the impeller of the wetend.

What parts make up a wetend?
Wetends basically have the same parts but the order of assembly can vary. But most common is this order: Plate/pump bracket attaches to the motor. In the middle of the plate/bracket is 1/2 of the mechanical seal. Next is the impeller that the motor shaft screws into. On the stem of the impeller is the other half of the seal. Next comes the wear ring. It floats on the nose of the impeller and rubs against the front of the pump. On some wetends this part is missing because the front piece has the wear ring molded into it. Lastly is the front of the pump with a large oring or square ring to seal the 2 parts. The whole wetend is compressed and sealed by screws or bolts. Some older wetends have no user replaceable parts inside the wetend so you must replace the complete wetend.