Firefighting crews were called to South Port soon after 6pm and left just after midnight, a Fire and Emergency New Zealand spokesman said.
The fire was on the 24m-length vessel MV Cindy Hardy, which is operated by Cruise Fiordland and can carry up to 10 passengers.
The fire was brought under control by 8pm, but crews remained there past midnight to dampen down any hot spots, the Fenz spokesman said.
It is understood to have originated in the engine room.
Fire investigators took a look at the boat yesterday morning.
Police had no information suggesting the fire was suspicious and were not investigating.
The website for Cruise Fiordland says the company has two vessels — MV Cindy Hardy, which operates in Fiordland, and MV Tasman Explorer, at Stewart Island.
Cruise Fiordland provides private charters and mixed-group scheduled cruises.
A Cruise Fiordland representative declined to comment yesterday.
MV Cindy Hardy was built in 1963 in Tasmania of Australian hardwood.
It has had a complete refit, including private en suites in each cabin, a new galley and passenger lounges.
By Grant Miller
