Yes. Get a Ferrite Choke from Radio Shack (or anywhere else
) and put it on the TV power cord. That should clear it up.
If it fails to then a more drastic approach is plugging the TV into a quality Uninterruptable power supply; although I'd sure this is easier said than done when talking about a boat.
All this assumes the shielding on your treadmill meets FCC guideline for EM emissions.
Try the choke first. They're cheap.