SS SIR WALTER SCOTT at Stronachlachar Pier.Loch Katrine,Scotland

SS Sir Walter Scott is a small steamship that has provided pleasure cruises and a ferry service on Loch Katrine in the scenic Trossachs of Scotland for more than a century, and is the only surviving screw steamer in regular passenger service in Scotland. It is named after the writer Walter Scott, who set his 1810 poem Lady of the Lake, and his 1818 novel Rob Roy around Loch Katrine.

In 1859 Loch Katrine became Glasgow's main water supply, connected by aqueducts and tunnels to the city more than 30 miles (48 km) away through a hilly landscape. The Trossachs became very popular in the Victorian era, and there were early steamship services on the loch. The Loch is surrounded by wooded mountains, and has romantic historical connections including the birthplace of the outlaw Rob Roy MacGregor. Queen Victoria had a holiday house built overlooking the loch.

William Denny and Brothers built Sir Walter Scott as a "knock-down" ship; that is, it was assembled with bolts and nuts at Denny's shipyard at Dumbarton on the River Leven, the pieces numbered and dismantled again, transported in pieces by barge up Loch Lomond and overland by horse-drawn cart to Stronachlachar pier on Loch Katrine and there rebuilt with rivets and launched. Denny's assembled Sir Walter Scott at their yard in 1899 and completed its reassembly and launch on the loch in 1900.

All ships in the UK must record a measured mile for seaworthiness. Sir Walter Scott completed its measured mile on the Firth of Clyde when bolted together, before being disassembled, transported to Loch Katrine and riveted together again.
Its original cost was £4,269, which included a delivery charge of £2,028.

Sir Walter Scott weighs 115 tons, is 110 feet (34 m) long and has a 19 feet (5.8 m) beam. It is powered by its original three-cylinder triple-expansion steam engine and has two locomotive-type boilers[clarification needed] which until the end of 2007 were fired by solid fuel fed into the firebox by a stoker. At a time when most steamers changed to oil-fired boilers, the Sir Walter Scott kept using solid fuel to meet the requirement of ensuring that Glasgow's water supply is not polluted, changing from coal to coke to reduce air pollution. In a refit at the end of the 2007 season the boilers were altered to run on biofuel. During this refit, the superstructure was rebuilt and a forward deck cabin was added. Some consider the modified superstructure an abomination, destroying the classic lines of this Victorian era steamer. The vessel has a crew of five.

Sir Walter Scott sails from Trossachs pier at the east end of the loch, 7 miles (11 km) north of Aberfoyle) and runs a ferry service 8 miles (13 km) west along the loch to Stronachlachar pier, in the morning and afternoon in spring and summer, taking walkers and cyclists who return by land, then takes those embarking at the pier and those doing the round trip back to Trosachs pier. In the afternoon it also does one or more shorter scenic cruises. In the winter it is taken up on a slipway for maintenance work.