Restoring Yamaha: Fuel Line Replacement And Engine Start Guide

Yamaha 115 is a powerful outboard motor that is widely used in boats. However, users often face issues with its fuel system, which can lead to starting problems. Common issues include fuel line restrictions, faulty fuel pumps, clogged fuel filters, and vacuum leaks. To resolve these issues, it is recommended to check and replace fuel lines, pumps, and filters, as well as verify strong spark on each cylinder. Additionally, draining the VST tank and inspecting the fuel cooler for proper water flow are important steps in troubleshooting fuel-related problems.

Check for bad fuel or debris in the gas tank

If your Yamaha 115 is not starting, it could be due to bad fuel or debris in the gas tank. This is a common issue with cars, and there are a few ways to check for and resolve this problem.

Firstly, it's important to understand the symptoms of bad fuel in your engine. These can include difficulty starting the engine, sputtering and hesitancy during ignition, issues with acceleration, an illuminated check engine light, and a rough or uneven drive. If you experience any of these issues, it is worth checking your fuel for contamination.

One way to check for bad fuel is to use a water detection probe. This involves lowering a probe to the bottom of your fuel tank. The probe has a colour-changing paste that will react if it comes into contact with moisture, indicating the presence of water in your fuel.

Another method is to take a sample of your gasoline and place it in a clear container. Allow the fuel to settle for around 30 minutes. Bad fuel or debris will often separate from the gasoline and sink to the bottom, forming a layer that you can visually inspect.

You can also add a small amount of windshield washer fluid to a sample of gasoline in a graduated cylinder. Shake the cylinder and wait for it to settle. Compare the amount of gasoline you put in with how much is left after settling. This will show the amount of alcohol in the fuel, which should be no more than 10%.

If you suspect that your fuel issues are due to a loose gas cap, ensure that you replace it and regularly check the seal to prevent debris and water from entering your fuel system.

If you find that you do have bad fuel or debris in your gas tank, you can resolve this by draining and cleaning the tank, then refilling it with fresh fuel. You should also use fuel additives to help disperse water and prevent future contamination.

Remember to always use high-quality fuel from reputable gas stations and ensure that you are using the correct fuel grade for your Yamaha 115.

Remove and blow out fuel lines with an air compressor

To blow out the fuel lines with an air compressor, you must first remove the fuel lines from their endpoints or attachments. Wrap a rag around the return line at the injector pump to catch any debris. Then, blow compressed air into the tank side of the return line. You can also blow air from the pump return end of the line, with the line open and not connected to the pump.

It is important to note that you should not blow compressed air through the fuel pump itself, as this could damage it. Instead, focus on blowing air through the fuel lines in both directions, ensuring that any debris is removed. You may need to change the rag a few times until no more particles come out.

Additionally, it is recommended to have extra fuel filters on hand, as any debris in the lines can end up in the filters. You may also want to consider installing an inline filter to collect any contaminants and service it regularly.

By following these steps, you can effectively clean out the fuel lines of your Yamaha 115 with an air compressor.

Test for vacuum leaks

To test for vacuum leaks on your Yamaha 115, there are several methods you can try.

One method is to use a can of carb cleaner and spray it around the intake manifold and hose connections while the engine is running. If the engine stumbles, revs, or stalls while you're spraying in a particular location, you've likely found a vacuum leak. It is important to exercise caution when performing this test, as you will be dealing with flammable liquids near a hot engine. Be sure to have a fire extinguisher on hand and perform the test outdoors with good ventilation.

Another method is to use a gas torch and a cylinder of LPG. Leave the torch unlit and start directing the flow of gas over areas you suspect may have a vacuum leak. If there is a leak, the LPG will get sucked in, causing the engine to run richer. You will hear a noticeable change in RPM when you've located the leak. As with the carb cleaner method, this test involves flammable gases, so ensure you have a fire extinguisher nearby and perform the test in a well-ventilated area.

Additionally, you can observe the ISC (Idle Speed Control) valve. Vacuum leaks on an EFI engine will lead to a higher than normal idle, and the ISC valve will close to an abnormally low percentage as it tries to adjust the idle speed to match the ECU map.

Finally, you can try spraying a substance such as starting fluid or LPG into the carburetors while the engine is running. If the engine starts running better, it is likely that you have a vacuum leak.

Check the ignition circuit

To check the ignition circuit of your Yamaha 115, you'll want to start by identifying the components of the ignition system and their functions. This includes understanding the wiring diagram and the colour-coded labels on it.

First, locate the Component Identifications (CIDs) on the wiring diagram, which will help you identify the components and their relationships. Then, look for circuit pathways, which indicate the direction of wire travel. Pay attention to power sources and related plugs as well.

Next, you'll want to test for spark. Use an adjustable spark tester to verify a strong spark on each cylinder. This will help rule out any issues with the ignition circuit.

Additionally, check for voltage output at the stator coils and CDI unit. You can refer to online manuals or a Yamaha tune-up guide for the correct output voltages. Ensure that the engine is running during these tests for accurate results.

If you're experiencing issues with the ignition circuit, it's recommended to test your meter on a known good engine to ensure accurate readings. Also, check for any shorts on the charge and trigger coils, as there should be infinite resistance between the single wires and ground.

Finally, keep in mind that Yamaha uses different terms for electronics than other manufacturers, so refer to their specific manuals and guides for accurate information.

Check the fuel cooler

Checking the fuel cooler on a Yamaha outboard engine is an important part of maintaining the fuel system and ensuring the engine's performance and longevity. Here's a detailed guide on how to check the fuel cooler:

Before beginning, refer to the service manual for your specific Yamaha 115 model to familiarise yourself with the location and components of the fuel system, including the fuel cooler. This will help you identify any potential issues.

Now, let's get started with the inspection:

• Locate the Fuel Cooler: The fuel cooler is typically found mounted on the back of the Vapor Separator Tank (VST). It is part of the fuel system that helps regulate the temperature of the fuel before it enters the engine.
• Visual Inspection: Start by performing a visual inspection of the fuel cooler and its surrounding components. Look for any signs of leaks, cracking, or damage on the fuel cooler itself, as well as the associated hoses and connections. Ensure that all components are securely connected and there is no visible fuel leakage.
• Check for Corrosion: Yamaha outboards are susceptible to corrosion, especially in saltwater environments. Inspect the fuel cooler and nearby parts for any signs of corrosion or buildup. Pay close attention to metal components, as corrosion can affect their performance.
• Fuel Filter Inspection: The fuel filter plays a crucial role in maintaining fuel quality. Check the fuel filter for any signs of clogging or debris buildup. A clogged fuel filter can restrict fuel flow and affect engine performance. Refer to your service manual to locate the fuel filter and its recommended replacement interval.
• Fuel Line Inspection: Inspect the fuel lines connected to the fuel cooler for any signs of damage, leaks, or blockage. Ensure that the fuel lines are intact, properly connected, and free from kinks or bends that could restrict fuel flow.
• Pressure Test: If possible, perform a pressure test on the fuel system to ensure that the fuel cooler and associated components are functioning correctly. This may require specialised tools and knowledge, so consider seeking assistance from a qualified marine mechanic.
• Check for Water Accumulation: Water accumulation in the fuel system can lead to significant issues. Inspect the fuel cooler and the VST for any signs of water accumulation or moisture. Refer to your service manual for guidance on draining moisture from the VST and addressing water-related issues.
• Fuel Quality Check: Yamaha recommends using high-quality, fresh fuel that has been treated with a fuel stabilizer and conditioner to prevent issues related to ethanol and water contamination. Check that you are using the correct fuel type and that it is free from contaminants.
• Regular Maintenance: Regular maintenance of the fuel system, including the fuel cooler, is essential for optimal performance. Follow Yamaha's recommended service intervals for fuel filter replacements and fuel system inspections. Carry out fuel system maintenance as outlined in your service manual.
• Seek Professional Assistance: If you notice any issues or abnormalities during your inspection, or if you are unsure about any aspects of the fuel cooler's function, don't hesitate to consult a qualified Yamaha marine technician for further guidance or repairs.

Remember, a well-maintained fuel cooler and fuel system will help ensure the reliability and longevity of your Yamaha 115 outboard engine. By following the above steps and staying proactive with maintenance, you can help prevent major issues and keep your boat running smoothly.

Frequently asked questions