Marathon Wood Furnace


New Member
Sep 5, 2019
Upstate NY
Hi all,

We bought a house last year with a marathon Wood/coal Furnace in the basement. I believe it is a logwood and at least 20-25 years old, but don't know much more about it. I tried to use it last winter with ok results... I haven't been able to find much info on how to use it. House is about 1700 sqft. It looked like it was never really used and just used as a backup.

The unit has a thermostat controlled damper, dual flues out the rear with a manual flue damper on the top most flue, clay lined brick chimney, and a Honeywell limit switch. There's a manual handle above the door which I believe is a bypass, but unsure which position (either in or out) is bypass mode.

The main problem is once a fire starts going, even with the all the dampers closed and smallest fire, the blower doesn't stop running and heat keeps kicking. It easily heats the house to 75-80+ and there's really no control over the temperature. The fan limit switch is set at about 120*.

There is about a 3" hole on the damper door, which I think is just to maintain the min burn rate. I tried limiting the hole with some aluminum duct tape in hopes to get more control over the heat output, but ended up with too cold of a fire and liquid creosote... Not good.

The other issue is getting smoke in the house. You can't open the door to add wood without smoke billowing out. I assume this is a draft issue. I did notice this summer the cleanout door on the chimney is broke and doesn't seal well, so that might be part of the issue. I've tried opening the flue damper and bypass, which helps but still get smoke in the house.

I'd really like to use it more and wondering there are any tips on how to properly use it. It's a really nice heat when it's going, but just too much! Any help is appreciated.