Robin,

Here is the link I was talking about that describes the different motors and their spec's;

http://www.bosunsmate.co.uk/british_seagull.htm


Here is the link to the company that has purchased the rights to 'Seagull'

http://www.britishseagull.co.uk/


The first site I listed offers this at the end;


My view of the Seagull
You either loved them or hated them. I have mended countless of these sturdy little machines in my time, and I have grown to hate them in an affectionate sort of way - like you would an alcoholic granny, who is a complete nightmare to live with but indispensable. They were very reliable motors until British Seagull were forced to modernise them in the 1980's by environmental pressures. Twist grip throttles, electronic ignition, cowlings, carb shrouds, better silencing and of all things, a reverse gear! They almost got it right by the time they ceased manufacture in Poole, Dorset, but by then their reputation had suffered, and the Japanese had caught up. The motors coming from Yamaha, Suzuki and Honda were every bit as reliable as the Seagull, and often more so, as well as being quieter, smoother, much more economic to run, and lighter. Unfavourable exchange rates meant that Seagull couldn't even beat the Japs on price, and so it was that eventually the factory shut down, with the rights to the name going to Sheridan Marine in Oxford. You can get in touch with them at http://www.britishseagull.co.uk - they also keep a lot of spares.

The main advantage of the old Seagull over the opposition was the fact they used no ball or needle races in the motor or the gearbox - all the bearings were turned phosphor bronze, which are not bothered by the odd bit of seawater or seaweed finding it's way in. A Seagull could be immersed when not running, to no ill effect, other than perhaps the fuel needing changing and the cylinder draining of water. Sometimes you might even have to clean the points, by simply undoing the big nut on the flywheel and removing the starter cord ring. In extreme cases, you might want to take the flywheel off, but no special tools were needed - the correct method is to turn the motor until the piston reaches bottom dead centre, hold the outboard up by the flywheel, remove the cord ring, replace the nut fully, and get your pal to bash the nut with a big club hammer! Really, this is the only way - use a puller and you risk cracking the flywheel.

No production Seagull was ever fitted with a reed valve that I am aware of, so a small amount of petrol was spat back out with every stroke of the motor - not very environmentally sound. Fuel consumption therefore was relatively poor.

Corrosion was not much of a problem because the alloy used was very resistant to sea water, even though no anodes were fitted. The iron cylinder block would gradually flake with rust in the water passages, but you could scrape these out, anneal the old copper head gasket, and hey presto! - your cooling was restored. The cylinder head on all the "square head" models had the legend "do not remove" cast onto them - this was because as the carbon deposits inside the motor accumulated, the heads ability to seal the compression chamber improved! You could guarantee that when you removed and replaced the head for servicing, a bit of water and compression would leak out for a while.
The water pump was particularly tough, as the rotor did not touch the sides of the pump housing in operation, but the top of the pump chamber could wear out causing water flow reduction. To fix this, mill a few thou off the housing where it mated to the gearbox. The other trick to boosting the water pump pressure is to replace the joint plate - the thick fibre gasket between the water pump and the gearbox. Only in extreme cases did the rotor need replacing, but this could be a problem as they sat on a ferrous steel shaft, which had to be scraped clean of rust before you sweated on the new rotor to avoid it cracking.
The gearbox was a wonder in itself - older models had no oil seals, and relied on the 140 grade oil staying in place purely because it was too viscous to leak. Saying that, you would always get a bit of oil collecting under the motor, as many irritated owners of cars with carpeted boots - trunks to you Yanks! - will testify. Seagull's own Makers Method bulletin #13 states "some oil must be able to pass through the bearings, and a little leakage from them is quite normal". Greenpeace loved this....
The Seagull's main attribute was the way it reliably delivered power - no high speed propellers for these beasts, but a high ratio gearbox transforming the miserable power output into very usable grunt. The Century Plus models had a huge 5 bladed fine pitched fan, as they called it, which would turn a meagre 4hp into enough thrust to shove along a 20 foot sailboat with ease. The most powerful Seagull ever made was the Kingfisher which appeared in the '80s - this was equivalent to an 8hp conventional motor, suitable for displacement hulls only.

The 2 worst faults of the older motors were the 10:1 oil mixing ratio, (which was reduced to 25:1 in the 80's by changing the carb needle on Villiers equipped models, or the main jet on the Amal carb models), and the noise levels. Boy, did these beasts smoke loudly!!

In summary, if you have one of these old motors then you have the perfect reserve emergency motor. Parts are likely to be available for some time to come, thanks to the efforts of Sheridan Marine and enthusiasts like John Williams. Just buy a packet of ear plugs, a lot of 2 stroke oil, and avoid motoring near any wildlife reserves!