These are all fresh water motors. We don’t even say the word out loud, S-A-L-T. I may pull off another cylinder and have a look. The rotors are new and fit well.
If the tube is plugged, would the water still exit the mid-section?

These are the aluminum castings. Three of my five motors have gotten very hot after a minute or so of running. I’ve stopped them or they quit at that time. Another one is apart and the last is a slick original I don’t want to risk hurting. Two of the runners do exhibit flaking paint on the cylinder from heat or the lack of primer. That paint isn’t discolored. They don’t look to have been stored outside or abused any more than normal wear and tear.
One interesting point, the best one has a tab standing off from the bock to stabilize the fuel line. A 1/2" by 2" piece of aluminum sheet the fuel line runs through to keep it from shaking. Painted the same color as the motor.

Looks as if the rotor pumps to a small oval opening which goes up toward the powerhead. Possibly lower unit grease or dirt is caking here restricting water flow. The 3hp models have a ‘water flush’ plug at this point. I will pursue this.