Kickstarting Your 2-Stroke: A Beginner's Guide To Boat Engines

Starting a 2-stroke boat engine can be tricky, especially if it's an older model. While newer outboards are similar to cars, with a simple tilt-and-key mechanism, older 2-stroke engines require more know-how. They can be temperamental, especially when cold, and it's important to ensure the engine has been properly serviced and maintained. This includes checking the fuel, spark plugs, carburettor, and tank ventilation. If you're considering purchasing a boat with an older 2-stroke engine, it's worth familiarising yourself with the specific steps required to start this type of engine.

Check the fuel level and shutoff valve

Before attempting to start your 2-stroke boat engine, there are a few things you should check to ensure the engine can run properly. One of the most important things to check is the fuel level. Make sure you have plenty of gas in the tank. While this may sound obvious, it is one of the most common reasons why a boat engine won't start.

Next, you should double-check that the fuel shutoff valve is set to "on". If the valve is not set to "on", gas won't reach the motor, no matter how full your tank is. If you have an external fuel tank, make sure the fuel line is properly connected to both the tank and the engine. You can do this by tugging on the line to ensure it is securely attached on both ends. If you need to, use a flat-head screwdriver to tighten the ring clamp connectors.

Inspect the fuel line for any kinks or cracks. Weather conditions can cause the hose to split, which can prevent a steady supply of fuel from reaching the motor. If the fuel line is split near either end, cut off the damaged portion and reconnect the line with its hose clamp. If the split is towards the middle of the line, you can use heavy tape to patch it, but make sure to replace the line as soon as possible.

If your motor has both an internal and external tank, check the switch and ensure it is set to the appropriate tank. It is easy to accidentally bump the switch while moving around on the boat or repositioning the motor. Additionally, make sure the tank vents are free from obstructions.

Check the fuel line

Checking the fuel line is an important step in starting a 2-stroke boat engine. Here are some detailed instructions to ensure your fuel line is in proper working condition:

First, ensure that your fuel line is the correct size for your engine. The size of the fuel line depends on the horsepower of your engine. For engines with 115 HP or less, a 5/16" fuel line is appropriate. For engines above 115 HP, a larger 3/8" fuel line is required. Using the correct size is crucial, as a fuel line that is too small may not be able to supply enough fuel to the engine, leading to strain on the fuel pumps and potential damage.

Next, verify that the fuel line is properly connected to both the fuel tank and the engine. Give the line a gentle tug to ensure it is securely attached at both ends. If you find any loose connections, use a flat-head screwdriver to tighten the ring clamp connectors.

Inspect the fuel line for any signs of damage. Look for kinks, cracks, or splits in the hose, especially near the ends. Harsh weather conditions can cause the hose to split, disrupting the steady supply of fuel to the engine. If you notice any damage near the ends, cut off the affected portion and reconnect the line with its hose clamp. For splits in the middle of the line, use heavy-duty tape as a temporary fix, but be sure to replace the line as soon as possible.

Additionally, check for any blockages in the fuel line. Some fuel hoses have a plastic lining that can break down over time, releasing particles that can obstruct the flow of fuel. To test this, disconnect the line at the motor and squeeze the bulb to force fuel through the line. If the flow is slow, the line is likely blocked and will need to be replaced.

Finally, pay attention to the fuel hose specifications. There are different types of fuel hoses designed for specific applications. For example, A1 hoses are used for feeding fuel from the boat's fuel tank to the engine and have a fire-resistant covering. On the other hand, A2 hoses are used for the fuel tank vent hose below the deck and do not typically hold fuel. Understanding the different types of hoses and their ratings will help ensure that you are using the correct fuel line for your application.

Check the spark plugs

Spark plugs are a key component of your boat's engine. They ignite a spark that fires the air and fuel mixture within the engine, creating the combustion that powers your boat. Therefore, it is important to check the spark plugs if your boat engine won't start.

Firstly, you should inspect the spark plugs for damage to the insulator tip, boot, and upper and lower insulators. Next, check for signs of fouling. A fouled spark plug is when the plug isn't burning fuel normally, which can cause damage to the plug and prevent the engine from starting. A normal spark plug will appear dry with a grayish colour. A spark plug with a white residue can indicate that the plug is too hot, while a black spark plug covered in soot can mean that the fuel has too much oil.

If you are unsure whether your spark plugs are working, you can test them. You will need a spark plug tester and a deep-well spark plug socket. First, test for electrical current by pulling off a spark plug wire and connecting it to one side of the spark plug tester. Then, place the spark plug tester at the top of the plug or a piece of unpainted metal that can act as a ground. Turn over the engine and look to see if a spark jumps across the gap in the tester. If it doesn't, the spark plug is not getting any power. If the spark is dim, it may not be getting enough power. A bright spark indicates a good current.

If you are still unsure, you can test the spark plug without a tester. Remove the spark plug with a deep-well socket. Reconnect the ignition wire to the top of the loose spark plug, then position the plug so the lower metal body is touching a metallic part of the engine cylinder head. Turn the engine over and watch the gap at the tip. If the spark plug is working, you should see an obvious blue spark. If there is no spark, or it is weak, the spark plug is likely to be the cause of your engine trouble.

Check the carburettor

The carburettor is a crucial component of a 2-stroke boat engine, controlling the mixture of oxygen and gasoline in the cylinders. It is essential to perform regular maintenance and checks on the carburettor to ensure the engine's performance and longevity. Here are some detailed instructions on checking the carburettor:

Firstly, it is important to understand the function of the carburettor. The carburettor mixes air and fuel in the correct ratio to ensure proper combustion in the engine. This mixture is then drawn into the cylinders, where it is ignited to power the engine.

To check the carburettor, begin by inspecting it for any signs of damage or leaks. Look for any cracks, holes, or loose connections that could affect the air-fuel mixture. Ensure that all hoses and connections are secure and in good condition.

Next, check for any blockages or restrictions within the carburettor. Over time, the carburettor can become clogged with residue or debris, affecting the engine's performance. Carefully inspect the jets, passages, and valves for any signs of blockage. If necessary, use a carburettor cleaner or compressed air to clear any blockages.

It is also important to verify the carburettor's adjustment. The carburettor needs to be properly adjusted to maintain the correct air-fuel mixture. Refer to your engine's manual for the recommended settings and adjust the carburettor accordingly. This may involve turning adjustment screws to fine-tune the mixture.

Additionally, pay attention to the condition of the fuel and air filters. Clogged or dirty filters can affect the carburettor's performance. Check and replace the filters as necessary to ensure a clean supply of air and fuel to the carburettor.

Finally, test the engine's performance after making any adjustments or repairs to the carburettor. Start the engine and listen for any unusual noises or behaviour. Observe the exhaust for any signs of excessive smoke, which could indicate an issue with the carburettor or the fuel-to-oil ratio.

By following these steps, you can effectively check the carburettor of your 2-stroke boat engine, ensuring optimal performance and prolonging the life of your marine vessel. Regular maintenance of the carburettor is essential to prevent issues and maintain the engine's power and efficiency.

Check the tank vents

When starting a 2-stroke boat engine, it is important to check the tank vents to ensure they are free from obstructions. This is because obstructions in the vents can cause fuel to become trapped in the line, starving the engine of fuel.

If you have a built-in tank, make sure the vent fitting is not partially blocked by an insect nest, wax, or any other substance. This is a common issue that can prevent the engine from starting. Check the vent for any signs of obstruction and clear it if necessary.

Additionally, when installing a vent hose, avoid creating sags or traps in the line. These traps can allow fuel to puddle, blocking the tank's ability to vent properly. The vent line should run as straight as possible to allow fuel to drain back into the tank via gravity.

It is also important to keep the fuel vent screen clean. Fuel vents often have fine-wire screens that prevent debris, insects, and spiders from entering. Over time, these screens can become clogged with corrosion, salt crystals, or grime, impairing the vent's ability to function. If the screen appears clogged, use a small wire brush to clean it. If the corrosion has eaten away at the mesh, it is important to replace the vent.

Finally, if your boat takes on a lot of heavy spray, consider covering the fuel vent with a clamshell cover to protect it from water intrusion. Water intrusion can occur in through-hull fuel vents, especially if they are mounted too low or angled forward. A clamshell cover can help deflect oncoming water and prevent water intrusion.

Frequently asked questions