I sort of don’t think the poppet is the problem. The water pump on that motor sends water up one tube and after passing through the power head the water is presented to the thermostat. If the water is warm enough the stat opens and the water is discharged and replaced by more water from the pump. But if is too cool the stat stays closed and the water pressure unseats the poppet and returns to the pump via the second tube for recirculation. You mentioned the second tube was not connected to anything. That ain’t correct. There were some changes made about that time. Previous models returned the water directly to the pump. Then they made a change that returned the water down to the bottom of the gearcase. Needless to say, the correct parts must be used.
The second tube was not connected when I pulled the gearcase because it was a long shaft tube. I don’t know what the previous owner was thinking. I replaced it with a correct tube which enters one of the two grommets on top/side of pump housing via #3 (impeller housing cap) on the parts diagram. There is also a third copper tube coming out the underside of the housing via part #3 and going to a grommet further down in the gearcase. Is that correct?
