British Seagull

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Lateral view of a Forty series British Seagull. The serial number dates it to 1954/1955
Forty Plus model British Seagull with recoil starter

The British Seagull Co Ltd was a British manufacturer of two-stroke outboard engines in Poole, Dorset from the early 1930s until the mid-1990s. Although their "Classic" engines were for decades an exemplar of rugged simplicity and reliability, the company eventually failed when customer tastes changed and as tighter emissions regulations took effect. The British Seagull company no longer manufactures complete outboard engines, but they continue to produce and supply spare parts from their Oxfordshire base.

A classic design[edit]

British Seagull outboards were first sold under the name Marston Seagull. They were developed at John Marston Ltd's "Sunbeamland" factory in Wolverhampton by development engineers John Way-Hope and Bill Pinninger. This pair later bought the manufacturing rights and marketed outboards as Bristol Seagull, later moving to Poole and settling for the name British Seagull.

The Seagull outboard motor had a simple single cylinder water-cooled two-stroke engine.[1] Atop the engine was a Villiers patented flywheel magneto[2], and on its port side was a simple carburetter with no air filter. Even a rudimentary rubber "storm cowl" was an optional extra, and induction noise when running was pronounced. Above the cylinder head was bolted a small brass fuel tank whose 10:1 fuel/oil mix was gravity-fed to the carb via a clear plastic tube that served to capture dirt particles in its U-bend. A simple plastic filter filter on the banjo union to the carb gave rudimentary secondary filtering, but it was still not unusual for the carb jets to become blocked. Starting was effected with a hand-wound pull-rope, although a recoil starter became an option in due course. Connecting the motor to the gearbox and propeller werere two downtubes, the forward one containing the drive shaft and the aft tube serving as the exhaust, which vented underwater. This arrangement meant that the engine could not be rotated 360 degrees as can more modern engines. The Seagull handbook advises that the engine can be safely run at full throttle (partly to prevent the spark-plug from oiling up) but adds that is wasteful to try to exceed the maximum design speed of a displacement hull, suggesting a "one-third open throttle" usually suffices.[3] The engines proved very rugged as they used high quality materials, and would last for years even in harsh marine environments and in developing countries.[4] Seagull outboards were utilitarian in nature with a relatively slow-turning prop, and so were ideal for use in dinghies, tenders and small yachts. The Silver Century Plus model could propel a displacement hull of up to 26 feet in length; but all Seagull outboards were unsuitable for high speed craft.[5]


An early engine of the company was the Model 102, developed from the Marston models of the 1930s. The Model 102 engines were fairly large and featured an integral engine cylinder block and head, with a water-injected exhaust. Some Model 102 outboards had a 13-inch-diameter (330 mm) propeller, gaining the moniker of "The Barge Pusher".

The model range for which Seagull is most famous is the "Classic" range. These "square block models" comprised the 64 cc Featherweight (aka Forty Minus) and Forty Plus, and the 102 cc Century and Century Plus. The Forty Minus and Plus used identical power units, but the Plus had a larger gearbox and propeller. The Century and Century Plus used even larger gearboxes and propellers. Classic model engines were produced from the late 1950s until the mid-1990s, and many examples are still in everyday use. The long life span is down to the high quality metals and the use of high-tensile bolts and studs.

In the early 1980s the factory produced a new series of British Seagull outboards, the QB series. The power units were developed by Queen's University, Belfast (hence QB) whose Mechanical Engineering Department specialised in modernising two-stroke design.[6][7] Painted black and sometimes known as the Irish Seagull, they featured quieter, more efficient engines, with a water-cooled exhaust and modified cylinder porting.

In the late 1980s British Seagull introduced two further models to their range, the Model 170 and the Model 125. Fitted with a cowling to enclose the engine, they featured upgraded carburettors and cylinder blocks. Both new models suffered from poorly designed crankshaft bushings, resulting in warranty claims against the company. Until that time the "Best Outboard Motor for the World" (as the marketing slogan ran) had an envious reputation for reliability, but these new models were never popular and they dented the company's image.

Towards the end of production a new model called the "5R" was introduced. The design of this engine was quite different from earlier models, using a conventional gearbox from a Yamaha 4HP outboard attached via an adaptor plate to a QB engine. These models were painted blue, the very last examples (known as "gold tops") having propellers and recoil starters that were gold-painted.

Fuel/oil mix[edit]

Models manufactured from 1931 to 1945 had a recommended petrol-to-oil mix of either 8:1 or 10:1. From 1942 models specified a 10:1 mix which was specified up to 1979. After that date a 25:1 mix was specified, which was again changed for the introduction of the models 125 and 170, but these engines with the 50:1 mix soon failed, and British Seagull again specified 25:1. This relatively high percentage of oil was necessary due to the way the crankshaft bushings worked. Early engines used short bushings, and later ones used longer bushings, hence the changes in oil requirement. The longer bushings were, in fact, used from 1967 onwards, and the engines from 1967 to 1979 can be used on the 25:1 mix by making carburettor adjustments.


  1. ^ "The Best Outboard Motor for the World" [1]
  2. ^
  3. ^ British Seagull Outboard Owners Handbook
  4. ^ Seagull maintenance [2]
  5. ^ Classic Boat Review [3]
  6. ^ QUB/Lotus/Jaguar 2-stroke research [4]
  7. ^ QUB 2-stroke development [5]

External links[edit]