Your engine is idle speed controlled by the timing. You can not simply move the timing levers. It takes a special ignition tool to set the timing on all the OIS engines. On yours the idle timing will end up being about 6*ATDC this will give you an in gear idle of about 700 rpm.
All idle speeds are measured with the engine in the water not on the hose. In the water you have the proper backpressure on the exhaust. Johnson/Evinrude also looks for in gear rpm, not neutral rpm for that motor.
The timing can be set on dry land, then checked in the water. You may find that once the engine is warmed up and in the water the rpm will drop to a proper idle.
Was the timing properly set after the engine was rebuilt? It MUST be set with the special tool.
The WOT timing is set in the same way. If it is too far advanced then you could damage the new rebuild. I would take the boat to a qualified shop and have the timing set. Double check the throttle shutters are closed all the way, put the boat in the water and see where the idle is.
Just by putting the engine in the water I would expect the idle speed to drop 300+ rpm, then another 100-200 in gear giving you a proper idle speed.
The other engine at 800 out of the water is too low. I would have the timing done on that engine as well.
Finally only check the idle speeds after the engines are warmed up with no starting spark advance.