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ere are our best answers to often asked questions including ideas to save you money, better understand your seagull outboard and enjoy the built in reliability of the Best Outboard for the World! And its all FREE thanks to the British Seagull Shop, Shoreline Wa. USA and the support of seagull owners around the world!

Charles A. Stearns – Authorized British Seagull Parts Stockist- Shoreline, A

15.I think I need a new coil – No spark!

16.What is the secret of Seagull Maintenance?

17.What is the fuel mix for my British Seagull?

18.How can I solve the electrolysis problems on my Seagull?

19.I have a pressed steel tank and its rusting – What do I do??

20.Capt Ron do you have an ebay store too???

22.The Greatest Evil with Seagulls…

23.How Exactly do I ship a seagull so that UPS doesnt destroy it?

24.Should I buy a new outboard or a used British Seagull?

25.Are there any books or manuals about British Seagull engines?

26.My metal fuel valve on my gas tank is leaking gas!!!


All seagull serial numbers start with a model code. For example FP stands for Forty Plus) If there is an L at the end of the model letter code this signifies a long shaft engine which in seagull land means that the engine is 6 longer than a regular shaft engine. From1963onwards a letter and number code is used to denote the month and year of manufacture. The month codes are as follows

Jan A, Feb B, March C, April D, May E, June F, July G, August H, September J, Oct K, Nov M, Dec N (Note I and L were not used in the month letter codes)

From1973 two letters were used for the month. With this serial number you can obtain parts and information on your engine. Its easy to make a mistake reading the number as all serial numbers were hand stamped. Sometimes a C looks like an 0 of an F might look like a P especially if the light is not good or the serial number is covered in grunge. For security purposes and to ensure you can obtain parts and information please copy your serial number down and keep it handy. IF you understand how the seagull serial number system works you will easily be able to identify a seagull and when it was built and also know other things about it like fuel mix, gear lube, and spark plug gap.Also because so many parts on seagulls are interchangeable it is some times possible that one motor was made up from several others and thats when you see very interesting mixes which do not appear to match with the serial number – for example a motor that was once a long shaft may now be a regular shaft engine because somebody has switched the lower unit at some time!

(Normally referred to as a 2 hp seagull, featherweight or forty-minus, these engines were also referred to as a 1-2 hp model when hp ratings were revised and then in later models they were rated in foot pounds of thrust i.e. the model 45 produced 45 foot pounds of thrust at the prop. Its easier to refer to them as a 2 hp !!! Many consider this model to be the best looking seagull as proportions are excellent and weight is quite low. They are a little harder to find than the 3 hp model because fewer were made)


Note on HP ratings:The HP ratings changed over the years. When you purchased the motor either from the original owner or from a seagull dealer you may have been told it was more powerful than the revised hp ratings now indicate. In past years there was great confusion in outboard hp ratings as different systems of measurement were used by each manufacturer. Legislation passed in the UK in the early 1970s resulted in revised hp ratings based on actual thrust at the prop. Confusion reigns supreme to this day on just how many HP seagulls produce. What confuses people is that a little 3hp seagull seems to have as much thrust as a modern motor twice its hp rating! Seagull has consistently advised that their motors are designed for displacement hulls NOT planing hulls where a higher speed motor is better.Just to add additional confusion to the subject if you are looking for a conversion factor between thrust and hp ratings forget it. There arent any. Horsepower is a measurement of work done. Thrust is a measure of static thrust. Why dont we all agree that hp ratings and seagulls dont go together and leave it at that! Naturally few will agree with that so here goes….

(Normally referred to as a 2 hp seagull, featherweight or forty-minus, these engines were also referred to as a 1-2 hp model when hp ratings were revised and then in later models they were rated in foot pounds of thrust i.e. the model 45 produced 45 foot pounds of thrust at the prop. Its easier to refer to them as a 2 hp !!! Many consider this model to be the best looking seagull as proportions are excellent and weight is quite low. They are a little harder to find than the 3 hp model because fewer were made)

(normally referred to as a 2-3 hp seagull, or forty plus or in later models as a model 55 they produce 55 pounds of thrust at the prop or approx 3 hp although to be precise one would need to refer to them as 2.5 hp+ models! The three hp or forty Plus was the workhorse of the seagull line with many made. It produces a surprising amount of thrust for an engine of this size and when you wind it up past 3/4 throttle it becomes a bit of a thrust beast!)


(normally referred to as a 3-4.5 hp seagull The 4,5 and 6hp seagulls all share the 102 cc large block. There is a huge difference between say a 2 hp featherweight and a 5.5hp long shaft with the big 11hydrofan on it)

(normally referred to as a 4-5.5 hp seagull and a model 110 and then a model 90 (reflecting foot-pounds of thrust), also previously referred to as a 6 hp nfusing isnt it!)


Silver Century Plus clutch model 80

Silver Century Plus clutch model 110/90 with reverse

The really old seagulls – the model 102

Occasionally we get requests to identify the older model seagulls called the 102 model. This model (equipped with a one piece round cylinder head) was manufactured for approx 35 years prior to the appearance of the classic square head seagulls (equipped with the square aluminum heads). Some model 102s were manufactured up to 1973 but most are older engines from the late 1940s and 1950s. The clutch drive models had a C in the serial number hence AC, TC, WC are clutch drive model 102s. The same letters were repeated with a D to indicate these engines were direct drive models ( i.e. no clutch) so we had AD, TD and WD. Finally the higher hp 102s were designated as 102 Plus engines and had an H designation hence AHC, THC and WHC letters appeared in the serial number. Although many parts are still available most of these engines are getting rather long in the tooth for dependable every day use and we see fewer of them each year. All use 140 weight gear oil and have the villiers MK1 ignition system.

There is a show on TV called theAntique Roadshowwhere hopeful people drag in stuff they have picked up at garage sales for pennies, and hope to find that it is worth thousands of dollars!! We all dream of doing this! We also get asked all the time What is my motor worth? We are not antique dealers. A British Seagull is a working motor. If you require a valuation of a motor from a collectable perspective, an antique dealer is your best bet for a professional appraisal of its value. Here is how we value a motor:

We cant do that without actuallyseeingthe engine and putting it thru certain tests. So there is no way to place a value on your motor without seeing it. That would be like phoning your doctor and saying Im not feeling well – whats wrong with me??? Less you doubt me, I have had owners approach me with engines that were described by them in good faith as being in good operating condition only to inspect it and find the blocks were cracked or major components were missing!Weneverplace a value on an engine without first seeing it, inspecting it and testing it and so if somebody has told you the British Seagull Shop said it was worth $xxx dollars then that simply is not true.

You can value your motor by considering the following:

4. What are motors like yours selling for on ? (Note – motors sold at an auction are generally sold as is and motors sold at a dealer are generally sold in good running condition. So, most motors sold at auction should sell for approx. 40-50% of the retail price since you are taking a risk that the motor may not be in good running condition.)

There are many ways to value a motor. A motor which was Gramps motor and is still in the family is, in our opinion, priceless. A motor (or spousal unit) that you had 30 years ago and still have today, is priceless. A motor that you took with you when you took your small sailboat to the South Pacific is … priceless. We understand seagulls, and putting a value on one is not something you do from a strict accounting perspective.

In summary -How much is my motor worth?- is a tough question unless I can see it and test it. If your motor is working and in good condition, take a look around at the cost of a new replacement motor of the same hp rating. A used motor of 10 hp or lesswill very seldom sell for more than 50% of the new replacement cost. The reason for this is that if a buyer decides to pay over 50% of the value of a new motor he starts to consider the advantages of buying new – the warranty- the fact that all parts are new- the fact that the latest technology is available, start to be factors in the buying decision. Hope that helps!.

Sadly, no. Since 1996 British Seagull no longer produces engines. The British Seagull Dealer network has been closed down. Parts continue to be available for most models via the parent company,Sheridan Marinein the UK, who has been very good about maintaining a spares inventory. British Seagull Stockists are also available in locations around the world. Stockists maintain an inventory of British Seagull parts and can order parts from British Seagull in the UK. Individual owners can also order directly from British Seagull UK. Supplying parts for motors which have been out of production, some for many decades, is a difficult and expensive task. On the good side, a British Seagull is one of the few engines in the world where you can still get parts for motors produced nearly half a century ago! One of the reasons that British Seagulls are no longer manufactured is that they were a high quality product that was relatively expensive to manufacture compared to more technologically-advanced motors built of cheaper materials. Very occasionally, we find a motor with very low hours on it and thats about as close as you will get to buying new.

There are three possible answers here. Please note that you MUST use the correct fuel mix for your motor or you will ruin it.The fuel mix MUST be fresh.As a rule of thumb a seagull can use more but not less oil.


A seagull needs this heavy oil film to lubricate large plain bearings, to raise compression and to accommodate the wide tolerances in the design of the motor.

NEVER LET THE FUEL SIT IN YOUR MOTOR FOR MORE THAN THREE MONTHS AS IT GOES STALE AND GUMS EVERYTHING UP. Some fuel gurus claim that mixed fuel goes stale after about a month depending on conditions and we have noticed in the shop that fresh fuel mix will start a motor when old fuel wont.

AChampion D-16can be used in all British Seagulls. If you have the Mk 1 and Mk 2 ignitions, then you use a gap of .020. If you have the Mk3 Wipac ignition, then your gap must be no less than .035 You should always carry a spare plug as it is the easiest fix on a seagull. Note that the very early seagulls – the 102 styles specified a gap of .015 to .018. This was due to the fuel used at the time and now a gap of .020 is recommended.

The Mk1 and Mk2 ignitions were made by Villiers and are found on most of the classic seagulls. The type 1 has a separate condenser. The flywheel on the Mk1 has three openings at the top. The Mk2 has a encapsulated coil and condenser. The flywheel on the Mk 2 has two openings at the top. An easy way to tell the difference is that the Mk1 is silver and the Mk2 flywheel is a gold colour. After 1978, the WIPAC Mk3 began making its appearance. This is a breakerless CD ignition system. These motors are sometimes called the blue caps as the top of the motor is …blue! If you have a seagull with the breakerless Mk3 system your plug gap is a minimum of .035.The flywheel will be silver. Finally the MK4 breakerless CD system is the one with a groove in the outer surface of the flywheel and it also is silver in color.

The original plug used in a British seagull was a champion 8 common. This big plug could actually be taken apart for cleaning. There was also a Lodge plug with a pink insulator that was used for a while. Its possible you will also find a champion D9 or D21 which is a different heat range than the D16.We recommend the champion D16 for all seagulls.You should have a spare plug and probably two because this is the easiest repair you can make to your ignition system. (They are offered on our ebay store in packs of two) When inserting the plug be sure to slightly lubricate the threads and use only your hand to start the thread. You really dont want to cross thread the steel plug threads into the soft aluminum head. Also do NOT over tighten the plug.

Maybe not!. When you are testing the cooling system in a seagull with a direct drive ( no clutch) in a small tank or bucket you need to take the prop spring and prop off. You also need to ensure that the water level is up past the gear box to about 2 inches up the down tubes (the drive shaft casing is the thin one – the silencer or exhaust tube is the fat one). There is a reason for this. A seagull has a hard plastic impeller. The older ones are aluminum. The impeller is fitted by a friction fit to the drive shaft which turns the prop. But, unlike nearly every other modern impeller design, the seagull impeller does not actually touch the pump body. The good part about this is that there is practically no wear on this part unless you operate in sandy water conditions. The bad part is that it will not pump a water & air mix and its not particularly good at pumping at 1/4 throttle and below. When you are testing the engine in a bucket, air will be mixed in to the water and the pump wont work. Note: if your motor has a clutch it is not necessary to take the prop off -simply put the gear shift into neutral. .

The exit hole for the cooling system is a pencil sized hole at the back lower surface of the cylinder block. When you have the engine started, you should get a nice clear stream of water at half and three quarter throttle and all is well. If not, back flush with a garden hose pressed against the cooling exit hole and try again.(you will get wet so ask the spousal unit to do it). Also try backflushing against the three horizontal slots in the exhaust housing where water enters the water pump area. (Dont back flush up the exhaust port as that leads into the cylinder and combustion chamber) Compressed air sometimes works too. What happens is that rust scale flakes off the inner surfaces of the water jacket and collects in the passages thus restricting water flow. By back flushing you remove some of the scale and re-establish water flow. You may not get very much water at slow speeds and this is something to think about. When operating at very slow speeds, your motor may not be getting very good cooling. You should increase the rpms of the motor every once in a while to ensure that cooling water is getting thru. At a certain point even back flushing will not re-establish water flow and thats when you need to disassemble the engine and remove the cylinder, then remove the aluminum head to clean it out. Although not terribly difficult it will take you a bit of time to do and there is always the problem of corroded fasteners breaking off etc. You really should purchase the service manual for this operation.

If you are operating the engine and notice there is no cooling water getting thru, STOP! Check for a blockage at the water inlet – perhaps a plastic bag or bit of kelp? There is a very good chance that an engine without cooling will crack its block. This is an expensive repair that can easily be avoided if you operate the motor correctly.

Please note that the 102cc seagulls (the 4,5,6hp) have many more problems with cracked cylinders than the 64cc seagulls ( the two and three hp models). So it is even more important to watch the cooling flow if you have the big block seagulls. From personal observation, the cracks appear to start on the bottom of the cylinder in the metal casting around the exhaust port and then cracks begin to appear in the water jacket are and they are then visible from outside. By this time the cylinder is toast …so to speak. My guess is that for every 10-15 large cracked cylinders I only see one small cracked cylinder!.

This depends on where you are going. A trip offshore for several months will require a different set of spares to be safe and prepared. Everyone should carry the following:

for pre 1979 engines. This can be difficult to find and you need the straight 140 type, not the multigrade. (140 gear lube offered on our ebay store)

that seagull makes. There are cut outs for various fasteners on the seagull including the dome nut and spark plug and its a very useful and simple tool to keep with your engine. You can find them on our ebay store too! A good idea is to tie a length of starter cord onto your tool and you have an emergency pull cord too!

When working on your motor, take it OFF the transom and place it inside your vessel as there is much less chance of dropping the parts overboard. If you are working on the carb you can take it off and work on it inside the boat. Trust me – this will save you lots of problems. Little parts seem to have a death wish and love to jump over the side to Davey Joness Locker!

One of the first things that you will notice when working on your British Seagull is that your tools dont seem to work! This can be disappointing especially to those with large and expensive tool kits. Its also one reason why some mechanics hate to work on them. British Seagull uses a British Whitworth thread pattern for all its fasteners. There are two major thread patterns the in world today- SAE and Metric. But in the years prior to 1973 the British used the whitworth thread on all their mechanical equipment including the British Seagull, the classic British Motorbikes like Triumph, Norton, BSA etc. and cars such as the MG etc.(Note the British also had thread patterns for motorcycles too and at one time had several thread patterns but we are trying to simplify the discussion here)

Sir Joseph Whitworth, an engineer, proposed this thread in 1841. This was the first standardized thread and quickly caught on in England. The principal features of the British Standard Whitworth (BSW) thread form are that the angle between the thread flanks is 55 degrees and the thread has radii at both the roots and the crests of the thread.. The British Standard Fine (BSF) thread has the same 55 degree profile as the BSW thread form but was used when a finer pitch was required for a given diameter. If only the British had called BSF BSWF much of the confusion with whitworth would disappear but oh no they called it BSF (with no mention of Whitworth). Seagull fasteners use BSF threads.

Update December 2004I received this email from Brian Eves in the UK last year and have decided to post it as he sounds like he understands the fastener situation better than most of us do so here goes ….( thanks Brian!!) If anybody else has some input on this please e-mail me and perhaps we can have the definitive answer on a topic that most of us find confusing!I suspect that a complete understanding of British Fasteners is something beyond normal human ranges of comprehension.

The reason for the confusion regarding BSW and BSF threads may result from the use of spanners the are marked with both treads. I have recently purchased some 1/4 and 5/16 BSF taps and dies which does confirm the thread size as being BSF. BSW is a much coarser thread, a good engineers website from the UK will give you the dimensions for each thread.

The seagulls use 11/4 x 1/4 BSF bolts to fasten the crankcase together, cylinder base are either 11/2 x 5/16 BSF studs or 11/4 x 5/16 bolts depending on what model. The studs for the tube are again 11/2 x 5/16 studs. I use cap screws to bolt the gear case to the pump flange, these are either 1/4 or 5/16 BSF.

Although the originals have a slotted head, i use the Allen Key type because using the right allen key there is no wear upon the bit that matters when you attempt to remove them. I have used a silicon sealant to cover the head and any hole at the base of the thread. -Brian Eves

Here is what I think is the final piece of the puzzle regarding BSW and BSF fasteners. The dimensions of the bolt heads and nuts are different for each thread pattern! This means that a 5/16 BSW socket will not fit a 5/16 BSF nut. However a 5/16 BSW socket is the same as a 1/4 BSF socket so will fit a 1/4 BSF nut. As you will realize right away there is a certain malevolent evil here, which on one level seems to defy any logic but which on another level allows one set of tools to be used on two thread patterns. Here are some sample equivalent sizes:

From a North American or European perspective when a mechanic picks up a SAE or Metric wrench he or she expects that wrench to fit the ONE size stamped on the wrench. The British mechanic knows that whitworth wrench will fit TWO sizes, BSW and BSF.

Just remember that your seagull uses BSF fasteners and that whitworth tools will fit but that a 5/16 BSW wrench will not fit a 5/16BSF nut.

You now know more about British Whitworth threads than you likely ever wanted to but it all boils down to this. The 55 degree thread pattern on your BSF fasteners means that normal SAE or metric fasteners will not fit on your seagull engine. And although the BSF thread is a whitworth profile that is it has a 55 degree thread pattern, the coarse thread BSW fasteners will not fit either. Oh and just to confuse things Seagull eventually went metric and the newest seagulls have metric fasteners on them. All the old ones are BSF. I will stop now! – Ron

Update March 12, 2005I received this note from Paul Isserlis and thanks Paul for the good info!

Am sure they carry on the 1/16 difference , tho they may jump to an 1/8 difference in larger sizes than Seagulls need. A story l heard was that they dropped the size of heads on BSF bolts to save metal in one of the world wars. Will leave it you to work out how much weight is saved on a seagull!

British motorcycles used whitworth w& f long after cars switched to american. In the late sixties BSA used whitworth , ces (cycle thread) , sae ,unc , and a couple of their own design just to keep things simple.

If you think of BSF as whitworth fine or BSWF its less confusing!

At this point anyone reading this FAQ on whitworth and seagulls will now have a much better understanding of the subject! As you see the key to understanding the muddled mess is that the seagull thread the BSF is the fine version of the whitworth thread pattern which is available as the BSW coarse pattern and the BSF fine pattern. Although whitworth tools fit each pattern the head and nut sizes between the BSW and BSF fasteners are different sizes so you cant use the same wrench for say a 1/4BSF and 1/4 BSW bolt. Thanks to Brian Eves and Paul Isserlis for helping us all out here! To prevent you having nightmares about this and waking up in the middle of the night screaming WHITWORTH!! keep a rubber mallet by your bedside and instruct the spousal unit to use it on your noggin should even the hint of the W word escape your lips…

BRITISH SEAGULL has a simple solution to the tool problem and offers an economicalone piece combination toolthat fits nearly all seagull fasteners! We have themhere

Oopps I did it again!!! Update August 26th 2005

Just when you thought you knew everything you ever wanted to know about the fasteners used on seagulls…..Apparently there is yet ANOTHER type of thread pattern on the British Seagull engine. While all the major fasteners are BSF (British Standard Fine) the ones smaller than 1/4 BSF are something called BA( British Association) threads. So that pesky little fastener on the fuel valve, the tiny thing on the silencer tube and the little rascal on the villiers carb are yes….BA threads.

British Seagulls are designed for displacement hulls only. They are a low-rpm, high-thrust motor, so have lots of torque but not lots of high-end speed. They work best with a displacement hull – that is a hull that displaces an amount of water equal to its weight while underweigh. (All boats displace their weight while at rest – thats Archimedes Principle.) A planning hull is pushed along on the surface of the water and often just a small portion of the hull is actually in contact with the water. With a displacement hull, the maximum speed is the square root of the waterline length in feet, multiplied by 1.5. For example, if your vessel was 25 feet long and had a displacement hull, the approx. maximum speed would be the square root of the waterline length, or 5, multiplied by 1.5. That is, it would be 7.5 knots. Examples of displacement hulls are dinghies, keel sailboats, workboats.

How can Seagulls have five HP ratings with only two block and piston sizes?

You may notice that Seagull produced several engines with different hp ratings but with only two block sizes and only two different pistons. Unlike other motors, I have been told that seagull measured its HP rating by the pull the motor could exert on a bollard. . There is a small block – the 64cc block that is shared by the two and three hp motors and then a 102cc block that is shared by the 4,5, and 6 HP motors. The gear ratio in the gear boxes and the size of the propellers determine the HP ranges within each block size. But remember horsepower ratings were measured differently over the years and it is difficult to say exactly how many hp each engine fact I ran across references to fractional hp ratings such as 1.5, 2.5, 4.5 and 5.5. Very confusing if one wants a single number. Lets look at some examples:

Both rated horsepower engines were generated from the same cylinder and piston.

The prop is very interesting. Its called a hydrofan and at first looks deceptively simple. But take a closer look and you will see not square blades but blades with a compound pitch to them. Seagull also provided a modern looking weedless prop of more conventional design. The 11 hydrofan on the 6 hp seagulls is awesome! Imagine a 37 pound motor swinging an 11 five bladed prop! No wonder they have so much torque!

5.5hp Silver Century Plus – has a 12:48 gear ratio, a five bladed 11 prop with an engine turning at up to 4000rpm. There is world of difference between the 26 pound forty featherweight and the big seagull – the silver century plus longshaft. But is it a 6hp , a 5.5 hp or a 5 hp? Who knows! ( in fact if anyone can explain this better than I can I will include the answer here!)

The huge advantage of keeping to only two block sizes is that many parts are interchangeable! A tremendous amount of excellent engineering went into your seagull. But dont go around spouting off gear ratios and prop diameters- a seagull is a working motor that likes to be taken out and used. Also, HP ratings changed over the years as different measurements methods were used. The bottom line is that your seagull with its lower gearing will provide a surprising amount of thrust at displacement hull speeds. And is there anything more fun than seagulling? Probably not! Well …maybe one thing.

(tank dry,bracket stripped for carrying)

(tank dry,bracket stripped for carrying)

(tank dry, bracket stripped for carrying)

(tank dry, bracket stripped for carrying)


Matching any outboard to a particular vessel without actually trying it is a surprisingly difficult question because of the number of variables involved including; local conditions, load, hull shape, hull weight, hull condition, use, etc. but we can offer the following general guidelines:




3HP A small dingy and a part decked 17 foot sailboat

3HP If you dont own a boat but carry a motor in your car for rented or borrowed boats

3HP As a second motor for fishing in 17 to 19 foot runaboats

4HP As a second motor for fishing for 17 to 26 foot runaboats

5HP As an auxillary for boats of 2 to 3 tons

5HP Full bodied boats , fishboats, scows 15 to 25 feet

5HP As an auxillary for boats 3 to five tons

In terms of mounting a seagull, you need13 of freeboardwith the 2hp models and15 of freeboardwith othe

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