jacky-
The
lines are probably interference, either emitted by the fans into the ship's power system, or broadcast into the air (RFI) and in either case showing up on your TV. Cheap motors can make that kind of interference easily.
A dc-to-dc supply might stop it--if the "noise" is coming over the powerlines. First, try running the fans and tv on totally separate power supplies, with no wire connections between them. (That means at least one on an isolated battery source.) If that makes the
lines go away...they can be filtered out with
line filters. If they are still there...no such luck, no cheap fix.