Need to know how to replace a water pump on 81 cj7

from thermostat hosing, through carby to heater core. other back to water pump

Do compression check. Probably blown head gasket. Chelly

25 TO 28 FOOT LABS

Fuel wire goes to the Gas Tank and Temp gauge goes to the thermostat located near the end of water pipe from radiator.

check this,
remove a convenient spark plug, stick it on it's wire and place where you can see it, stick you finger over the spark plug hole and have a friend crank the engine, note whether the air blast and spark are the same instant if not the distributor's out of time

Take out the thermostat and run it like this for while. If the motor still over heats: Look over by the battery, do you see where those two hoses from the radiator and the water manifold are going into the firewall? Take the hose going to the manifold from the firewall off of the connection at the firewall and connect it directly to the water pump. I think the manifold hose is the one on the right just make sure it's not the one coming from the water pump. You'll have to remove the hose coming to the fire wall from the water pump where it is connected at the pump but, that's OK for now just tie/tape it to something out of the way. Now then, your water pump will be sending water directly to the water manifold without any obstruction. When you run the motor for a little while and find that it stays super cool, I then suggest (if you want any heated air this winter) that you have the heater core (there behind the firewall where the two hoses were going) flushed clean or replaced and hooked back up. Once water can flow freely through the system your thermostat can probably be reinstalled w/ out overheating the motor.

check to see if u have 12v at the pick up coil in the dist. if not thats ur prob. my 81 cj7 304 v8 did it

the axle joint?

Well, assuming that the water pump is turning the correct way, looks like you are going to have to pull the radiator out & take it to a guy who cleans radiator interiors. Seems to me that you may have some sediment built up and the water is not circulating thru the rad. This would explain why the top is warm & the bottom cool with no thermostat. Whilst the rad is out, flush the block with water. See what comes out. Don't use a "flush kit" just yet. In my experience, the flush kits that you buy are not good for this issue, have it done by a pro, but, after he cleans it, then get a flush kit & flush the block anyway. If there is sediment in the radiator (from sitting), there is def sediment in the block.

The timing would have to be WAY OFF to make it overheat.

check your fuse, if good check or replace headlight, if that is good then check the headlight switch, easy to change. good luck