Tips & Tricks

These tips & tricks 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.
* 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. Note, using a mineral oil will deteriorate the spark plug faster than a synthetic oil.
* Use a premix oil ratio between 10:1 & 16:1. Compared to 25:1 ratio, this can have 3x benefits;

1. better hold the combustion pressure, &
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.
* Leaking fuel taps can be re-corked. Alternatively they can be replaced with ball type valves.
* 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.

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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 rebuild it
* 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 1000~2000rpm, 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 around 4000rpm~5000rpm. Often the standard propeller is pitched outside this rev range. This results in a less than optimal output
* 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.

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

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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 anti-cavitation (anti-ventilation) plate may allow you to raise the motor a little further without the propeller sucking down air from the water surface. ie ventilation. This is best done by substitution of the thick pink water-pump gasket with a 3.0mm aluminium plate

* 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 optimised with the bottom of the hull

* Like all outboards, the Seagull produces propwalk. The seagull has a right hand screw prop. Propwalk on the Seagull tends the transom to the starboard. With the outboard straight ahead, the boat would tend to turn into a lefthand curve. (Prop-walk is an entire subject in itself)

Therefore;
With the motor mounted in the centre of the transom, it’s actually crooked, from a physics & thrustline & drag point of view. The boatwould tend to ‘crab slightly semi-sideways, an inefficient use of power. Fitting fins or strakes is an energy consuming solution to this characteristic
Suggestion;
Try off-set mounting the motor a few inches to the portside. This might produce more speed. However there is a downside. Depending on your hull-shape & dynamics, then, off-set mounting might experience a poorer ‘wake factor’. The result could be a speed reduction.

* 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 by using the tilt pin.

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

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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.

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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 & emulsifiers. 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.

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Ignition Tuning

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

* What we commonly face with the good-ole Seagull outboard is that the spark plug fouls regularly. Often a carbon whisker forms across the electrodes, bridging them. This shorts the ignition & stops the motor. It’s very annoying having to change the plug out on the water. The problem of carbon whisker formation is caused by a number of critical factors, including that the spark is partially shrouded from the combustible mixture by the ground electrode itself. This is usually the most practical factor to address. You can effectively eliminate this whiskering problem by shortening the ground electrode & shaping it to an asymmetric point.
* 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 (but without touching) the flywheel magnets by adjusting the mounting. The laminations can be slotted to better this. 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.

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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 or 420 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.

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Easy Motor Starting


* 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.
* Move the coil laminations as close as possible to (but without touching) the flywheel magnets by adjusting the mounting. The laminations can be slotted to better this. 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.
* Practical on the water testing of these ideas will reveal the best solution for your hull & motor combination.

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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.

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Disclaimer:

By taking any action based on any of the ideas expressed here You are thereby agreeing to the following;
1. The material contained here is purely opinion & does not constitute any form of advice
2. You acknowledge this text may contain factual errors
3. Before performing any such or related activity You agree to prior seek & follow independent sound competent advice
4. You agree to have investigated all matters pertinent to the subject
5. You agree to act on the basis of Your own judgment & experience
6. You acknowledge the no-hopers & free-loaders who choose not to take responsibility for themselves for the need for disclaimers such as this

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