The simple direct questions are: Can I run two hot water heat boilers off the same thermostat? Both boilers are currently ran off their own thermostat, but it wouldn't be hard to run a thermostat jumper wire from one boiler to the other and then just disconnect the 2nd thermostat all together. Is that something I can do and not cause a problem with anything?

The long story is: The house was built as a mirror image, ranch style, side by side duplex in the mid 1950s. Everything was separate between the two sides. Somewhere around 25 years ago it was opened up into one house. One kitchen was removed, and they removed most of the wall between the living rooms of the two sides (where both thermostats are located). The utilities were all merged together, but the heating and plumbing is still largely separated with the exception of one of the water heaters that was removed and the two hot water systems were connected through one water heater. Around 5 years ago a complete new AC system was installed and ran off one thermostat.

Last winter, both of the 1950s dial thermostats were replaced with digital thermostats. Since then we have had inconsistent heat. Either one side was hot and the other was cold, or vice-a-versa, unless it was really cold, then both sides functioned well. This would be if both thermostats are set at the same temp. The thermostats themselves are about 10' apart on the same pretty much open wall. if we bump either stat up one degree, that side is warm and the other side is cold, especially in the more separated rooms. I believe I would be better off is both boilers ran off the same thermostat so both turned on and off together.

Seeking educated opinions please.
Thank you, Gene