Regan Brown
Keeping your fuel lines clean is an essential part of outboard engine maintenance. This is especially true for older engines, such as the Mercury 650, which are more prone to problems caused by deposits in the fuel lines. In this article, we will cover the steps to clean the fuel lines on a Mercury 650 outboard engine, including checking for leaks, replacing old fuel lines, and using fuel additives to prevent and remove carbon deposits, gum, and varnish build-up.
| Characteristics | Values |
|---|---|
| Engine type | Mercury 650 outboard |
| Engine details | 4-cylinder, 65 hp long shaft |
| Problem | Fuel delivery issues, potential leak or bad check valve |
| Possible solutions | Rebuild fuel pump, check primer bulb, replace fuel lines, check for cracks in lines and fittings |
| Additional advice | Look for loose connections, consider replacing all rubber lines, use a fuel stabiliser for long-term storage |
| Related issues | Air in the lines, water contamination, fuel oxidation |
| Cleaning products | Mercury Quickleen, Mercury Quickstor Fuel Stabiliser |
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What You'll Learn
Check for water in the fuel lines
Water in the fuel lines of your outboard motor can cause internal damage and be very costly. It is important to check for water in the fuel lines regularly, especially if the boat has been exposed to rain or condensation. Here are the steps you can take to check for water in the fuel lines of your Mercury 650 outboard:
First, locate the fuel filter. The fuel filter may be hidden in a compartment, so refer to your boat engine's owner's manual if you are unsure where to find it. Once you have located the fuel filter, disconnect the line running from the fuel tank at the fuel filter. Drain out a couple of pints of fuel into a clean glass jar. You can also use a repurposed food jar for this purpose.
Let the fuel sit in the jar for about 30 minutes. Water is heavier than fuel, so if there is water in the fuel, it will settle at the bottom of the jar. After 30 minutes, check the fuel in the jar. If there is a clear bubble at the bottom, this indicates water contamination. The bubble may appear as a gelatinous white layer if there is phase separation due to ethanol and water mixing.
If you suspect water contamination, you can confirm it by using a water-finding paste. Apply the paste to a wooden dowel and insert it into the fuel tank. If the paste changes color, it indicates the presence of water. However, this method may not be very accurate in determining whether it is water or phase separation.
If you find water in the fuel lines, it is important to take action to remove it. Siphon the water from the bottom of the tank using a hand pump. You can also hook up a temporary tank with known good fuel to your engine and disconnect the fuel line from the fuel pump to the carbs, then crank it over with the kill switch pulled.
To prevent water contamination in the future, there are several measures you can take. Firstly, try to consume the fuel and don't leave it in the tank for extended periods. Fill your tank with enough fuel for your next trip and refill it for the subsequent trip to keep the fuel fresh. Secondly, use ethanol-free gas (E0 fuel) if possible, as ethanol in blended fuels attracts and absorbs water molecules. If you must use gasoline containing ethanol, add a marine-specific fuel stabilizer to reduce the water absorption rate. Additionally, regularly inspect, clean, or replace your boat's fuel filters as per the recommendations in the owner's manual. Finally, when winterizing or storing your boat, fill the fuel tank to capacity to prevent condensation from forming inside the tank.
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Use a marine-rated fuel stabiliser
Marine fuel stabilizers are an effective way to clean the fuel lines of your Mercury 650 outboard. They are designed to prevent issues in the fuel system and engine, and can also be used to address existing problems.
Marine fuel stabilizers are a popular choice for boat owners as they are a simple, yet effective solution to maintaining the quality of your fuel and the performance of your engine. They are particularly useful for preventing issues during the winter months when boats are often stored away. By adding a marine fuel stabilizer to your fuel tank, you can stabilize the fuel and prevent issues caused by ethanol-attracted water from entering the fuel tank. This, in turn, prevents carburettor clogs and fuel pump failures.
To use a marine-rated fuel stabilizer, simply pour it directly into your fuel tank prior to filling up with fuel. The amount of stabilizer required will depend on the product and the size of your fuel tank. For example, the STA-BIL Marine Fuel Stabilizer recommends using 1 oz of stabilizer for every 10 gallons of fuel. It is important to follow the instructions on the product you are using to ensure correct usage.
In addition to stabilizing your fuel, marine fuel stabilizers can also provide other benefits such as improved engine power and fuel economy. They can also protect your engine and fuel tank from corrosion, ensuring the long-term health of your boat.
When using a marine-rated fuel stabilizer, it is important to run the engine for a few minutes after adding the stabilizer to allow it to treat the entire fuel system. This will ensure that the stabilizer is effectively cleaning and protecting your fuel lines and other components.
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Clean the fuel tank
To clean the fuel tank of your Mercury 650 outboard, it is important to first drain the tank and clean it thoroughly. This is because, over time, fuel can begin to oxidise, forming a gum-like substance that settles in the tank and can cause engine problems.
One way to do this is by using an additive such as Mercury Quickleen or Quickstor. Quickleen contains aggressive cleaners that remove carbon deposits and other gunk from the tank and fuel system. It also helps prevent engine knocking and piston seize-up. Quickstor stabilises fuel and keeps it ready for use when taking your boat out of storage. It is recommended to treat fresh fuel with this additive before storage to prevent fuel breakdown and oxidation.
Another way to clean the fuel tank is by using a high concentration of Sea Foam Marine PRO. Add a full can of Marine PRO to a low tank of fuel (around 1/4 tank) and operate the engine for at least 20 minutes before refuelling. This will help clean the injectors and fuel system.
Additionally, it is important to keep your fuel tank covered when not in use to prevent water contamination. If your fuel does become contaminated with water, you will need to empty the tank, clean it, and then hook up a temporary tank with known good fuel to your engine. You can then disconnect the fuel line from the fuel pump to the carbs and crank it over.
Finally, it is recommended to keep your fuel tank filled with fresh fuel, especially if you have an older boat with a vented fuel tank. This helps to reduce the chances of condensation forming in the tank.
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Check the primer bulb
To check the primer bulb of your Mercury 650 outboard, begin by locating the bulb itself. It is likely attached to the fuel tank via a check valve. Once you have located the primer bulb, inspect it for any signs of damage or wear. If the bulb appears cracked or brittle, it may need to be replaced.
Next, try priming the bulb by squeezing it firmly. A functional primer bulb should be firm when squeezed and should quickly rebound to its original shape. If the bulb feels soft or does not rebound properly, it may be defective or damaged.
It is also important to observe the behaviour of the primer bulb while the engine is running. A properly functioning primer bulb will not remain hard or primed during engine operation. This is normal behaviour, and the bulb may become slightly softer as the engine runs. However, if the bulb becomes completely soft or loses its prime, it may indicate an issue with the bulb or another component in the fuel system, such as an air leak.
To further diagnose potential issues, you can try replacing the primer bulb with a new one. If the problem persists, it may be necessary to inspect other components, such as the fuel pump, fuel lines, or the carburetor. Additionally, consider consulting a qualified marine mechanic for more comprehensive troubleshooting and repair advice.
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Check for cracks in the fuel lines
Checking for cracks in the fuel lines of your Mercury 650 outboard is a crucial step in ensuring the engine's performance and safety. Here are some detailed instructions to guide you through the process:
Begin by locating the fuel lines on your Mercury 650 outboard. They are responsible for transferring fuel from the tank to the engine and are usually made of reinforced rubber to prevent kinking and splitting. Given that your engine is an older model, pay close attention to the condition of the fuel lines, as they are more prone to deterioration and damage over time.
When inspecting the fuel lines, look for any visible cracks along the exterior of the hoses. These cracks indicate potential weaknesses and can lead to fuel leaks. Bend the flexible pipes between your fingers to feel for any splits or cracks that may not be visually apparent. Fuel lines are often located under the engine, making them susceptible to corrosion and damage from knocks or debris, so be sure to check these areas thoroughly.
Additionally, check the fittings and connections of the fuel lines. Loose connections or faulty fittings can lead to leaks as well. Feel around the joints for any wetness, as fuel may run along the pipe before dripping. If you notice any wetness or visible fuel leaks, it's important to address them immediately.
If you identify any cracks or leaks, it's recommended to replace the entire fuel line. Improvised joints or repairs may not be effective in the long run, and the safety hazards associated with fuel leaks are significant. Rubber hoses can dry out over time, becoming more brittle and prone to leaks, so it's crucial to prioritize their inspection and maintenance.
Finally, when working with fuel lines, always prioritize safety. Disconnect the battery to prevent stray sparks, and avoid any open flames or cigarettes during the inspection process. Keep a fire extinguisher nearby as an added safety measure.
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Frequently asked questions
To clean the fuel lines on your Mercury 650 outboard, you should first check for any leaks or bad check valves. If there is a leak, you may need to replace the fuel lines. If the lines are old and cracked, they should be replaced regardless. Once you have addressed any leaks or cracks, you can flush the fuel lines with a fuel treatment product such as Mercury Quickstor Fuel Stabiliser or Quickleen.
There are a few products that can be used to clean the fuel lines on a Mercury 650 outboard. Mercury Quickstor Fuel Stabiliser can be added to fuel before long-term storage to stabilise the fuel and keep it ready for use. Quickleen can be used to remove carbon deposits from injectors and carburettors. Sea Foam Marine Pro can also be added to the fuel tank to clean injectors.
To prevent clogging, it is important to keep your fuel tanks clean and to periodically check them for water and sediment. You should also check your fuel filter often, as fuel filters help prevent fuel contaminants from entering your engine.
