All You Ever Wanted to Know About the British Seagull But Were Afraid to Ask

The following information may be of use to you:

Technical Information and Repair Manuals:

The best manual I know of, the Clymer Manual, is out of print but is available used every so often at eBay.  Other than that, there are the Seagull Service Manual and technical specification sheets (I believe still available from Seagull, in England,, and the many Owner’s Manuals and Owner’s Spares Books that were issued with new engines, usually available used at eBay.  There is also an excellent repair manual “The Classic British Seagull” (available in print or CD versions) offered regularly via eBay, or directly from the author, Don Meyer (e-mail address:

Some of the places where you can also obtain Seagull information and parts:

Seagull Forums:

Seagull Racing?

Believe it or not, seeing is believing.  Take a look at:

And last but not least, for a bit of soul searching on those trying days:

LIVING WITH A SEAGULL (or Zen and the Art of Seagull Engine Maintenance…)

Fuel Valve Repair:

If leaking, the fuel valve can be repaired using a set of four O-rings.  The O-rings, in my repair method, are of the following size: 3/16″ ID (0.1875″ or 4.7625 mm) x 3/8″ OD (0.375″ or 9.525 mm) x 3/32″ CS (0.09375″ or 2.38125 mm).  You can read a description of the complete procedure, along with some photos, at or   There is also some other information on Seagulls in that page.

In terms of chemical resistance to gasoline/oil, the ideal O-rings compounds are Buna-N (Nitrile) or Viton.  Click on the following for a link to the O-rings I currently use:

You need four O-rings for the repair.  The above link leads to a reputable (and with reasonable prices) source of these O-rings for the fuel valve repair:

The O-ring Store, LLC
222 Thain Rd
Lewiston ID 83501
Phone 208-413-6377
Fax 208-413-6719

Important Technical Information


Fuel Mixture Ratios


 Gear Oil

To find out what is the proper grade of oil to use in the gear case, visit:

Check the preceding link to determine the correct grade of crankcase oil (not grease) for your Seagull.  The recommended oil in the gear case for some engines: SAE 140 gear oil for regular use, SAE 90 gear oil for cold weather, and even engine oil under freezing conditions, but never grease; change the gear case oil every 15 hours of running time.

SAE 140 is what trucks use in their differential.  Available at an auto parts store or where truck parts are sold.  Some automotive stores can possibly have it or order it for you.

You will note that this crankcase oil mixes with the water as the gear case is not totally sealed.  This is normal.  That is why the oil changes color, and the reason for the need to change it every 15 hours of use.  If the oil mixture has thickened so much, possibly due to extended storage, then perhaps some engine degreaser or grease solvent could do the job, but I do not know it that would do more harm than good.  I would prefer to just use fresh gear oil, of the recommended type, spin the engine so it warms up, and then pour the mixture out.  Repeat the operation as necessary.

Water Pump

Make sure that water comes out of the exit port under the piston housing when the engine is running half-throttle and faster.  If you are idling, water will stop coming out, but this is normal.  Just ensure that everything is OK by opening the throttle so as to reestablish the water circulation every so often.

Difficult Starting

If the engine is cold, use the choke mechanism.  When warm, the choke is not necessary.  If the Seagull does not start in 3-4 pulls of the cord, STOP, do not keep trying.  You will only make matters worse.  Inspect the park plug and clean or replace as required.  If you smell gas, remove excess fuel from the carburetor by pulling the cord with the fuel valve shut off and the HT lead disconnected.  This is a good time to check the HT lead for any problems.  Beyond that, the next suspect is the condenser points, as they may require cleaning and or adjusting.  At this point, if nothing has worked, call it day and a mechanic, and go home to watch some TV!

Leaking Carburetor

From the carburetor or the float chamber?  Flooding is typically because of a needle that sticks in the float chamber.  I recommend that you get one of the Seagull manuals I recommended to you earlier, as the repair can produce more damage than good if not done correctly. Perhaps start with minimal disassembly and squirt in some carburetor cleaner.

Please note that if you turn off the engine, shut off the fuel valve, and then tilt the engine, fuel will leak, but this is normal although undesirable.  What you need do is to shut off the fuel valve prior to arriving to the dock/buoy so that the fuel in the carburetor/float chamber is used up.  Of course, do this only if you absolutely know that you will have power all the way to your destination.  According to the original owner’s manual I received with my 1968 Seagull, this is a mark of good seamanship!

According to the current standard-bearers of the British Seagull:

(Excerpted from

“All British Seagull outboard engines should run on unleaded petrol.

Did you know that unleaded petrol does not store for as long as standard leaded petrol – so keep it fresh.

As soon as you mix Two Stroke Oil with the petrol it shortens its useful life.

These factors together with natural evaporation of the petrol from an oil mixture are the most common problems in re-starting your engine after the winter or a prolonged period of non-running.

Fuel tanks and, particularly, carburettor bowls are left with an oily sludge in their base – as soon as you start your engine, even with fresh fuel, the sludge moves and blocks the carburettor or oils up the plug.

Remember to drain the fuel completely prior to the winter (or period of non-running) and use fresh fuel mixture in the spring.

What drowns a Seagull?

Apart from fresh fuel (as above), it is the corrosion caused by storing the engine somewhere warm, after use in salt-water, that does the damage. Usually cleaning the magneto and coil contacts and cleaning and re-gapping the spark plug and contact set is sufficient to regain the spark.

The second most common cause of bad starting is simply exhaust backpressure, caused by having the engine too deeply in the water, so that the exhaust gases are unable to escape. The correct depth of the propeller is with the exhaust outlet about an inch or two (25-50 mm) below the surface of the water… deeper immersion will affect both starting and performance.”

Recommendations from my Circa 1968 Seagull Owner’s Manual:

  • The less you take apart in the engine, the better.
  • Do use the right plug, and always carry a plug spanner.
  • For some vintage engines, the recommended oil in the gear case: SAE 140 gear oil for regular use, SAE 90 gear oil for cold weather, and even engine oil under freezing conditions, but never grease; change the gear case oil every 15 hours of running time.
  • The correct fuel:oil mixture: the older engines use 10:1, that is, ten parts of fuel to one part of oil; use regular low-octane gas.
  • Do keep an extra spark plug with you at all times, along with some extra propeller springs and cotter pins, and changing the high tension cable (spark plug cable) every few years helps wonders.
  • A bracket can be used to adjust the depth of the engine in the water.
  • ALWAYS secure the engine with a lanyard.

If you follow these simple rules, your Seagull will last you for as long as you want to, and then some… if you can put up with the noise and smoke!

Hope all of this helps.

Happy Seagulling!


Angel Enrique Pacheco, Ph.D.
Silver Century Plus Fixed Drive # SP1718D8
Comprado nuevo el 23 Junio 1968
Purchased new on 23 June 1968

De Santo Domingo, República Dominicana, viviendo en Brampton, Ontario, Canadá

From Santo Domingo, Dominican Republic, living in Brampton, Ontario, Canada


© 2018 Angel Enrique Pacheco, Ph.D.  All Rights Reserved.





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