intrigued

[cahillp3]

goes well with a pint too

[markhld]

Charlesuk,
thanks i do need glasses, just like the barmaid in the pub who thought you looked liked a certain someones father.
i can still spot a bargain or two
Markhld

[Keith.P]

The thing that I cannot understand is.
Its a seagull race, but most with modified engines to the extent that they may only just resemble a seagull externally but internally it bears no resemblance at all.
Its like having a vintage VW beetle with a Porsche engine in the boot, how far do you go until its its not a seagull anymore.
I can understand the boat design part of the racing seagulls, but not the engine part.

[Charles uk]

When you've worked on as many Centurys as I have you'll realise that seagull must have made 10 different cylinder head castings, 4 or 5 different cylinders, pistons, conrods, crankshafts & crankcases.
Some of which combined with certain of the others have a positive result on the power output of your century.

So we blue print them, perfect bearing clearances, all the components working as they were designed to do, using all the best Seagull parts that you feel will make a positive contribution to your final power output.

It works, ask Blue, I could tow his boat faster than his 102+ could push it.

Mine is good, but there are quite a few that are better, not here but in Bermuda & New Zealand.

[Horsley-Anarak]

The thing that I cannot understand is.
Its a seagull race, but most with modified engines to the extent that they may only just resemble a seagull externally but internally it bears no resemblance at all.

I want my engines to look like a stock engine, but with loads more grunt.

When you look at the internals of a Seagull compared to other similar aged engines, you realise there is room for improvement
(give Charles a ring and he will run you through it).
It is not hard to make them go better, but it is very hard to make them very quick. Also it can be very expensive to make them very quick.

I am going down the try to understand what is going on and adjust route. Using standard Seagull bits to make it go better.
You get funny looks if you use a seagull nowadays, but even funnier if they think you are going too fast.

Ever since the first internal combustion engines, people have been trying to make them go faster.

At least with Seagulls a bit of racing fun can be had cheaply.

When you consider that for the price of 5 Gallons of petrol you can still buy an engine to use in a race, there can't be many racing activities that are so cheap.

All we need is more venues, like they have in NZ. Let us hope that more suitable stretches of water can be found.

This is just a century, no special bit just tweaked a little. I goes much better, which puts a smile on my face.

Simple pleasures.

H-A

[livewire]

As i see it, it's all each to there own. If someone has the time, inclination and money they can modify any item to their hearts content. We all need hobbies to get us out from under the wifes feet. Or as i see it our own quality time.

Personnally i like "Old" stuff and i like it original. Be it cars, bikes and engines. But i do suffer from OCD so personnally i like to build,repair or fix things to the best standard that i can. Where possible i would like to make things better than "New" and operate it ito t's full potential.

It makes me think back to the days when i would watch my wifes uncle race hill climb (Time trials). You would have a whole range of cars, Triumph TR3 - TR7's, Super 7's, Porche Turbo's, little race cars which went like stink. Even one bloke who had some old ex formula 3 car.
His car was a Triumph TR7 with a Dolomite Sprint engine which was healily modified. (I know a TR7, not may peoples cup of tea) But it was a cheap shell which when he crashed didn't matter too much.
On one extreme i saw people drive there beloved Triumph TR3 to the track, then they removed the windsheild and placed the race visor in. As well as swapping the road tyres for slicks and race it for the day. Then put it all back and drive home.
One thing that did happen is they all raced within there "Class"

Oh when i mentioned my OCD i don't really have it. But i do clean, paint and over engineer whenever possible.

Maybe one day i'll even buy a boat.

[outboard]

Intigued I am. Having read this thread I'm inclined to see the fun involved. Charles mentioned changing the Century, can things be done to modify a 40+? Not that I'm eperienced enough to do this yet, but it might be something for the future.
Have you looked at the lochs of Scotland for a venue, there's plenty of nice places with nice surroundings for camping?

Gerard

[Charles uk]

I'm the man who builds Church's I only wrote churchs because I can't spell Cathedrals when I blueprint my Seagulls.

I have worked on less than 10 of the 40 series so I can't really comment. buy yourself a book on two-stroke tuning & come up with your own ideas.
Make sure everything is working perfectly before you start.

Remember it's easy to get fuel into a two-stroke but air is more important as you need to burn that fuel!

[outboard]

Thanks Charles. Any ideas on specific good books? I'll certainly get more eperience with my 40s before I tackle anything more.

Gerard

[Horsley-Anarak]

If you search for 2 Stroke tuning there are a couple of book.

Here was a link to one

http://

H-A

You will need to do your own detective work.

[outboard]

H-A, your the man! Thanks for that, it's most appreciated.

I promise you guys, I'm going to turn up at one of the events and buy you a beer. Yep, I know it's hard to believe "a Scotsman offering to buy beer", but you guys never stop amazing me with your help.

Gerard

[smersh]

Big Seagull race tomorrow! I cruised the circuit today with my 40 Plus but can't make it tomorrow. Beaut river setting, but I don't have water cannons or enough eggs to throw...

A Mum showed up today in a ute(small pick-up) with 2 teenagers, a tinny(alloy dinghy) and 5 Seagulls(great outboards)! They tried out the motors one-by-one and chose the fastest 2 for race tomorrow. I helped them with starting instruct's which I originally got from this web site.

Race info:
http://seagulloutboard.com/

Pics from last year; incl police Seagull boat:
https://www.facebook.com/album.php?aid= ... 0717899360

[livewire]

Ah taking info from the link Smersh just posted...

Seagull Outboard Tips & Tricks


These tips are ideas contributed by a variety of Seagull Outboard enthusiasts & based on actual practical working experiences. Interestingly, going better often doesn't involve extracting more power from the engine. Rather, the winning formula is one of achieving reliability & reducing drag through the water.

Fuel:

* If your fuel is more than a few weeks old, then, replace it with fresh fuel. Perhaps tip the old stuff into the car to avoid wasting it.

* Try aviation-gas or high octane race-gas, (if you can get either).

* Try out pump-gas of a different brand. Suggestions: Gull / BP Ultimate

* Change your premix oil from the thin modern 2 stroke oil (TCW-3) to a motor lube oil like ordinary SAE 10w40. This can improve the seal at the crankcase bearings. This allows the engine to better develop crankcase compression, especially in worn motors.

* Use a premix oil ratio between 10:1 & 16:1. Compared to 25:1 ratio, this can have 3x benefits;

1. increase the combustion chamber compression, &

2. increase the crankcase compression, &

3. reduce the unwanted blow-by, especially in worn motors.

* Setup a remote fueling system. This will save time & improve safety during fuel top-ups on longer ocean voyages.

* Setup a clear external fuel filter. There are 3x benefits to this;

1. clearly identify any water contamination,

2. observe the presence or absence of flow

3. eliminate dirt ingress to the carb

Avoid these 5x commonly made mistakes with an external fuel filter

1. improper flow direction, filters are direction sensitive

2. use of opaque or translucent filters, you can't see what's going on

3. failure to remove the fuel-tap gauze, leaving the fuel-tap gauze in place often restricts the flow too much

4. use of restrictive designs, paper elements are often unsuitable, gauze or sintered block elements are best

5. downward flow, ideally have the filter flow upwards to expel air, horizontal is okay

* Practical on the water testing of these ideas will reveal the best solution for your motor & hull combination.



Propeller:

* File the leading edges of the blades to a sharp edge. This creates a finer entry for the blades through the water. Be sure to remove material only from the forward facing face (& not from the thrusting face).

* If the prop has worn or damaged tips, then, replace it or have it rebuilt

* Balance your prop. Strangely, British Seagull the manufacturer, didn't seem to balance their propellers very well, (if at all). It's usually found that standard propellers can be hugely out of balance. Given your prop spins at around 1000~1500rpm, this means alot of power is going into making vibration rather than thrust. In many cases, there can be more vibration coming from an imbalanced propeller, than the motor itself.

* Select a pitch for your propellor that optimise's the engine to run at 3800~4000rpm. Often the standard propeller is pitched too low resulting in the engine over-revving. This over-revving causes the engine to lose efficiency & produce less power

* In your Seagull outboard, the prop drive spring is retained by a washer & split pin. You can improve upon this system with a quick release re-useable 'R' type clip. There are 5x benefits to upgrade to this system;

1. no tools required to replace the drive spring

2. avoids the temptation of re-fitting a used split pin

3. these clips have been endurance tested & have proven to be trustworthy.

4. makes propeller changes a breeze

5. suits all 'Classic' Seagull models.

* Have your local propeller builder custom build you a prop.

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Mounting Setup:

* Raise the motor as much as possible from the water so as to reduce viscous water drag & effectively increase the exhaust tube working volume

* Fitting an anticavitation plate may allow you to raise the motor a little further without the propeller sucking down air from the water surface. ie ventilation

* Improve your wake factor. If your propellor is exposed to a disturbed flow of water, then, you are said to have a poor wake factor. Re-position your propellor to an undisturbed flow of water to better your wake factor. This would apply, say, in a tunnel hull boat, where, lowering the motor to a clearer flow of water has been proven to increase speed. Also, this would apply, say, in a deeply keeled boat, where, off-setting the motor to a clearer flow of water has been proven to increase speed.

* Adjust the tilt angle by moving the thrust block in or out, so, the propeller axis is parallel with the bottom of the hull

* Through bolt the transom bracket. This lessens the risk of the motor jumping off the boat when you strike an object or ground the motor. You can still fit & remove the motor readily by using the tilt pin.

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Exhaust:

* Like most 2 stroke motors, there can be a tendency accumulate carbon deposits in the exhaust port. These accumulations restrict the exhaust gas flow. Remove the exhaust tube & scrape clean the exhaust port of any carbon build up. Be extremely careful not to burr the cylinder wall or deposit any scrapings into the cylinder.

* If you have a standard shortshaft motor, then, increase the exhaust tube volume. The most practical way to achieve this is to change to a longshaft motor. This practice is particularly effective on the 2.5hp models

* Raising the motor also has the effect of increasing the effective exhaust tube volume.

* If You have a square block model, then, divert the cooling water discharge into the exhaust tube. Set this up similar to the 102 model. This will cool the exhaust & reduce the unwanted back pressure slightly

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Gearbox:

* The biggest gearbox problem by far is internal corrosion. The manufacturer recommends heavy gear lube oils like EP-140 or SAE-140. These oils have 2x major issues;

1. they don't address the corrosion problem faced in the real world, &

2. they create alot of internal viscous lossess that reduce useful power to the propeller

The manufacturers reccomendations were made with the best knowledge & materials of the day, but, that era that has been surpassed. Oil technology has advanced hugely including, the use of dispersants & friction modifiers. Unlike gear oils, modern engine lube oils contain dispersants. These give the oil better ability to suspend leakage water as a relatively harmless homogenized solution. Without dispersants the water has more tendency over time to separate out from the emulsion. So given all this, use a thinner oil such as ordinary modern engine lube oil SAE 10w40. Note that thin oil also tends to leak out faster & leak water in faster, this is especially the case in worn gearcases. Important you change it after every outing.

* The ordinary modern engine lube oils like SAE 10w40 will reduce internal viscous losses resulting in greater useful power to the propeller.

* Don't use grease. It can't suspend leakage water & is extremely viscous.

* Fashion a fairing cone to the front of the gearbox, so as to create a finer entry to the passing water

* File the leading edge of the skeg to a sharp edge. This creates a finer entry to the passing water

* Removing the skeg can be risky, as the propellor will have less defence against striking objects.

* If you have a square block motor, then, changeover your gearcase to a model 102cc type gear-case. These present a finer entry to the passing water. ie, less drag. The most practical way to do this is put your square block power head onto model 102cc outboard frame

* If you have a 4.5hp motor, then, don't use a high thrust gearbox. Convert to a standard gearbox. High thrust gearboxes are identifiable by their large 11"~12" diameter propellers. Motors setup with these gearboxes were often referred to as 'Barge Pushers'. These barge pusher gearboxes tend to be better matched to heavy hulls of several tons & are generally unsuitable for achieving speed

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Ignition Tuning:

* Renew your spark plug with a Champion D-16 or NGK AB-6 & gap it to 0.020"

* The contact points should be scrupulously cleaned & polished with 600grit wet & dry sandpaper. The correct gap is 0.020". This is absolutely crucial for two reasons. Firstly it affects the dwell angle & thereby the coil magnetic saturation level. Secondly this affects the ignition timing

* If you are having trouble with oil contaminating the contact points, then, you can fit an oilseal to upper crankshaft. The most practical way to do this is to glue a seal onto the outside of the upper main bearing using expoxy.

Seal fitting Tips,

1. remove the crankshaft key & put sticky tape over the keyway so as to protect the seal from being 'nicked' during fitting.

2. spread a very light film of oil over the crankshaft only

3. Clean all mating surfaces thoroughly with thinners before gluing

4. After the epoxy has thoroughly cured, then, spread a drop of oil around the seal lip

* Flywheel removal is best avoided where possible. However, for an explanation of the recommended technique click here

* Test the true performance of your ignition by removing the spark plug & gaping it to 0.060", then rotating the flywheel only by hand. This increased gap simulates the resistive load experienced by the ignition system when the spark plug electrodes are subjected to normal cylinder compression. The flywheel rotation by hand simulates the cranking speed at the peak of compression

* Move the coil laminations as close as possible to the flywheel magnets by adjusting the clearance in the mounting. The electrical output of the coil is proportionate to the inverse of the mathematical square of the separation gap between the laminations & the passing magnets. Basically this means a small reduction in the lamination gap will greatly improve the ignition output. This is a little known secret to make the engine start easily

*Check the plate on which the ignition is mounted is firmly fixed to the crankcase. The fixing of this plate is crucial to the correct ignition timing & unfortunately it tends to get bumped when lifting or transporting the motor.

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Carburettion:

* If you have a Villiers carburettor, then, adjust the needle height to optimize the performance

* Also, if You have a Villiers carburettor, then, fit a rubber storm hood to the bell-mouth intake, this reduces both rain & water spray ingress.

* If you have the Amal 416 carburettor, then, re-jet it. Often the original factory set jetting can be less than ideal. This has been found to be the case particularly when you encounter low barometric pressure or your elevation exceeds 1000ft.

* Dismantle your carb & scrub it clean. No end of trouble & un-reliability can be caused by accumulations of dirt & muck in the carb. Similar applies to your fuel tank.

* Should you find dirt & muck in your carburettor, then, check your filter gauzes are in good order & not missing.

* Setup a clear external fuel filter. There are 3x benefits to this;

1. clearly identify any water contamination,

2. observe the presence or absence of flow

3. eliminate dirt ingress to the carb

Avoid these 5x commonly made mistakes with an external fuel filter

1. improper flow direction, filters are direction sensitive

2. use of opaque or translucent filters, you can't see what's going on

3. failure to remove the fuel-tap gauze, leaving the fuel-tap gauze in place often restricts the flow too much

4. use of restrictive designs, paper elements are often unsuitable, gauze or sintered block elements are best

5. downward flow, ideally have the filter flow upwards to expel air, horizontal is okay

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Starting Easily:

* As your motor wears, then the cylinder compression gradually declines. If the compression in your 4.5hp engine is below around say 45psi, then, you can begin to experience poor starting & overall performance. Exchange your block/piston/rings assembly for a rebuilt unit

* In cold weather or sub-zero conditions the fuel can struggle to vapourise. You want to heat the cylinder head & base of the sparkplug. Slowly tip a kettle of boiling water between the tank & flywheel getting it to flow over the head. Alternatively, remove the spark plug & heat it over 100degC with a blowlamp.

* Avoid these 5x commonly made mistakes with your starter rope;

1. a cord too long, may not release (real injury risk!)

2. a cord too short, will give a low cranking speed

3. a cord too fat will wedge in the spool

4. a cord too thin can bunch not release smoothly

5. an improper handle will not give a firm grip

An optimized starter rope will be diameter 5.5mm x 650mm inside length

* Basically there are 2x types of ignition. Villiers 2x pole & Wipac 3x pole. The Wipac 3x pole offers a technically superior design. It's possible to convert a motor from Villiers to Wipac by exchanging both the entire mag-plate assembly & flywheel assembly.

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

Boat Hulls:

Basically there are two types of hull. Displacement hulls versus planing hulls. The dynamics of each type are quite different. Displacement hulls push their way through the water while planing hulls skim over the surface.

* Displacement hulls have a maximum efficient hull speed. Beyond this, they consume large amounts of power with little speed gain. This maximum efficient speed is approximated by this formula;

(Maximum Efficient Hull Speed in Knots = 1.34 X Square Root of the Waterline Length in Feet)

Basically this means the longer the hull, the faster it will go. This explains why the rowing skiffs you see in the Olympic games are so long & pointy

* Change to a boat with a lesser hull width. This reduces the hulls' 'wetted' area, (& therefore drag)

* Planing hulls want a minimal 'vee', as, the flatter the 'vee', the less the energy needed to push them forward.

* In all cases, reducing the weight of your hull will reduce viscous losses. It's practical to make / find a hull less than 30kg

* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

[livewire]

As that last post was quite large i've split it in two. Here's the next section.

How to Get More Power


1. Porting ~ optimisation of port heights & sizes & understanding time areas.

2. Exhaust ~ calculate expansion chambers, headers & tuned pipe lengths.

3. Squishbands ~ understanding the interplay with detonation.

4. Compression ~ know the preferred ratio & BMEP value.

5. Fuels ~ discover octane boosting & oxidising fuels & oxygen scavengers

6. Induction systems ~ solve values for flask resonance effects & carb size

7. Reed valves ~ work out flutter & length & synthetic materials

8. Crankcase compression ~ learn of it's significance & ideal ratio

9. Ignition ~ how to improve efficiency by advancement of the timing



Despite the Seagull outboard being simple in design, achieving significantly more power is quite difficult. Basic 2-stroke theory is quite simple. However, the finer internal working principles of the 2-stroke engine are quite complex. The developmental research is thorough & now well documented. By having a comprehensive understanding of the inner working theory, you'll be able to modify your engine for significantly more power. Expert performance tuners share their knowledge & experience & secrets in the following explanatory books.

[Charles uk]

You forgot these books,

* Two-stroke Tuner's Handbook by Gordon Jennings
a copy of this will cost you £50 + but good & applicable.


* Two-stroke exhaust systems by Roy Bacon
good but not a lot of use £10.

* Design and Simulation of Two-Stroke Engines by Gordon Blair
you'll need a master in applied mathamatics to open this one £400ish.

* Two-Stroke Performance Tuning by A. Graham Bell.
similar to Jennings but a bit more modern, good £15 ish.