Eureka! I figured it out!
This motor was given to me by fellow who had been given the motor by somebody else. He had absolutely no history to pass on. I have been tinkering with it for months. I finally got it to run but it always overheated. No water coming out with the exhaust. I replaced the pump rotor, the water tube grommet, confirmed that all water passages were open, but still no water came out with the exhaust. Several times while it was running, I removed the drain plug at the base of the head to observe how much water was being pumped. There was always a lot of hot water spewing out under air pressure around the plug threads as I loosened the plug, followed by a flow of cool water when the plug was removed. I began to wonder why was the hot water under pressure and spewing back in the wrong direction from what I thought the flow should be. I again removed the head and also the carb. I traced what I thought should be the water flow and then I found it. The passage through the exhaust cover connected to the carb was blocked by the gasket. Both the water inlet and outlet that directs the water to the exhaust were blocked. I used my office hole punch to punch out two holes, reassembled and started the engine. Warm water spewed out with the exhaust from the holes in the midsection as it should. The carb stayed cool and no percolation!
Someone sometime in the past had installed the wrong gasket. It was a perfect fit, but it blocked the water passages. See pictures attached. The holes that I punched are indicated by arrows. The gasket looks factory, not homemade. Maybe for a different model?
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