I ran the 45 gph Meziere for ever. One thing I did that helped is I tapped the hole in the housing under the thermostat. put a plug in it and drilled a 1/8th inch hole in the plug. that was good for about 10*
And did the water just pour out or what? I think you stopped short in your explanation.
The 45 gpm pump he's referring to is the drop-in pump that fits the stock housing (same one I have). There is a bypass hole underneath the thermostat in a stock housing. You tap it for 3/8" npt (no need to drill), put a pipe plug in it, then drill a 1/8" hole through the plug. This is def. worth doing...dropped mine about 10° also. It reduces the amount of hot water that's recirculated through the motor.
