phantom,
I'll have to take a tape to mine, but it is installed under the workbench in the engine room of our sailboat. Probably 30-some inches long, maybe 18" wide and maybe 24" high. In this particular application it has a raw water pump pushing through a heat exchanger and then into a "wet" exhaust (far quieter).

If you're on dry land you'd need the one with a radiator.

Our is old school so you always know when it's running. When we're anchored we run it at night to run the reefers and watch a movie, then kill it until morning when we fire it up so we can shower, etc.

My neighbor has one which wheezed up. His replacement runs inside a dampened box. You can have a conversation next to it.