Mercury Transoms & Exhausts

Mercury Transoms and Exhausts Resources and Information

Transoms and exhausts are essential parts of every functional outboard engine. PartsVu is proud to stock a wide variety of certified Mercury transoms and exhausts to fit your Mercury outboard motor’s exact specifications. We also offer a selection of Mercruiser engine mounting hardware.

We also regularly publish helpful resources to help you maintain your Mercury outboard motor, such as:

• Mercury Outboard Engine Schematics
• Mercury Outboard 100-hour Service Guides
• Mercury Outboard Serial Number Lookup

Mercury Transoms and Exhausts FAQs

How does an outboard exhaust work? 

In an internal combustion engine, exhaust is produced every time combustion takes place. Like any other exhaust system, Mercury marine engine exhausts are necessary to carry the exhaust out of the engine. Most outboard engine exhausts expel exhausts under the water to muffle the sound and cool the exhaust.

How do I service my Mercury 4-stroke outboard fuel system?

Use a filter wrench to loosen the existing filter element and use caution when removing it as it will be filled with gasoline. A clear plastic or glass container is helpful to dump the filter and examine the contents. A small amount of debris is common, as is a small amount of water after the fuel has had a moment to settle. More significant amounts of water would warrant further investigation.

Move back to the engine and locate the filter element(s) on the engine. The scope of this service will only include the low-pressure fuel filter and fuel water separator if applicable by model. Mercury recommends that owners do not service their high-pressure fuel filters. Depending on your engine model, the water separator filter (or castle filter) may be removed by using a wrench, standard tools, and a little caution. Unplug the water-in-fuel sensor if applicable and spin the cap off of the housing. Replace the filter element with a fresh one, lube the o-ring with grease or oil, and carefully reinstall the cap.

Locate your Mercury engine’s primer bulb if applicable and use the primer to pump up the fuel system. You should feel and hear gasoline entering and filling the filter cup. Check for leaks and prime until the bulb becomes firm.

If you are not already regularly running Mercury Quickare and/or Quickleen through your Mercury fuel system, the 100-hour service interval is an excellent time for a “shock treatment.” Quickare is a fuel system cleaner and top-lube that will help to clean deposits from the tank, lines, carburetors, injectors, and pumps. It breaks up fuel system varnish and will help to prevent gumming.

Quickleen is a fuel system conditioner that also helps to remove carbon deposits. The standard dose is one ounce per ten gallons, but if you are not running the product regularly, you can double that ratio for more cleaning power. Pour the products into the fuel tank fill and run the boat. No additional work is needed. It is a great idea to inspect your fuel tank fill’s o-ring for damage when you add fuel or additives as a damaged o-ring can allow water from rain or boat washing into your fuel system.

How do I perform an oil change on my Mercury 2-stroke outboard motor?

Engine oil selection is critical to long life, so review the information in your owner’s manual to make certain you are using the correct products. Not all TCW3 oils are formulated the same, and different Mercury models do prefer specific oils. Mercury Marine offers a wide assortment of engine oil – both in blend and additives. If you are uncertain exactly which oil is best for your application, consult your owner’s manual.

If you do locate contamination in the oil tank, use a vacuum extractor to pull the remaining oil out of the tank for proper disposal. While good quality two-stroke oil is certainly expensive, running contaminated oil can lead to catastrophic failure. If you have never cleaned the bottom of your tank, prepare to be surprised by what you find.

Several laboratories provide performance testing of used oils, allowing you to learn more about the health of your engine. Blackstone Labs is one such provider, and they have a convenient mail-in kit that includes everything you need to submit an oil sample. They can also test gear oils, hydraulic fluids, and oils from your other vehicles or toys. Oil test results can tip you off to an accelerated wear condition inside of your engine long before any other symptoms show up. If you still want to know more about your engine, purchase an oil filter cutter and open the spent filter to look for evidence of contamination and metal dust or shavings.

How do I perform an oil change on my Mercury 2-stroke outboard motor?

Spent engine oil can be removed from the engine by extraction or via the oil pan drain screw plug. The extraction method requires the use of a vacuum extractor which is inserted down the dipstick tube and uses suction to pull the spent oil from the pan. Oil extraction tends to be very clean and is probably the most widely used among marine technicians. Alternatively, the drain screw itself can be removed. Be sure to have plenty of drain pan capacity as some engines can hold up to seven quarts of oil. We also recommend an oil absorbent pad like the 3M HP156 pad to catch any errant drips that might soil your driveway or lawn.

In cold climates, it may be helpful to start and warm the engine before draining the oil to thin it slightly. However, if possible, perform the engine oil change as the first part of the service since the maximum amount of oil will be in the oil pan already from the engine sitting allowing you to extract as much old oil as possible to minimize contamination of your fresh oil.

As the old oil is draining, you can work on removing the engine oil filter. Depending on your specific Mercury model, your filter may have a drain lip that helps to keep the mess to a minimum when you unscrew the old filter. However, most older engines do not have this feature. We suggest being prepared with plenty of absorbent rags or placing a small cup that is cut to size below the filter before removal. Using a PartsVu Maintenance Essentials filter wrench is the best way to loosen the filter. Remember when you reinstall the filter, over-tightening will only make your life more difficult when you are ready for the next service. Some technicians puncture the old filter allowing trapped oil to drain back into the block before removal, but this will ruin your ability to take the filter apart for further inspection.

Once you have inspected your spent oil and filter, set them aside for proper disposal. If you removed the drain screw to empty your oil, carefully reinstall the drain plug. The new oil filter should be removed from its package and the o-ring lubricated with a thin coat of fresh engine oil. Spin on the new oil filter and gently tighten to seat the o-ring without over-torquing.

Why should I use Mercury fuel additives?

Quickare treats and stabilizes fuel at every fill-up which is necessary because just about all gasoline today contains up to 10% ethanol. Left untreated, ethanol-blended fuel can break down leading to gum and varnish build-up which causes internal engine corrosion. Fuel additives such as a bottle of Quickare keep fuel fresh between fill-ups for up to three months.

The second step within Mercury’s fuel care system cleans your engine and fuel system. All combustion motors develop carbon deposits and the best way to clean those deposits is to add Mercury Quickleen to your fuel tank. Simply add a bottle of Quickleen to your outboard fuel tank once per year to remove carbon deposits, prevent engine knocking, piston seize up, and extend spark plug life. Aggressive fuel system cleaner within Quickleen works to quickly and thoroughly remove carbon deposits from carburetors and fuel injectors, intake valves, spark plugs, piston crowns, and cylinder heads.

Likely, there are periods when your boat is stored or is used infrequently, which can lead to issues with your engine running. If your boat will be sitting for an extended period of time, you need to add a fuel stabilizer like Mercury Marine Quikstor to prevent both regular and ethanol-blended fuels from breaking down, oxidizing, and causing fuel system corrosion, and eventually affecting the engine’s performance. Before storage add a bottle of Quickstor to your fuel tank, then run the engine so that the treated fuel circulates throughout the engine and fuel lines. This extended fuel stabilizer prevents gum and varnish from forming in the engine, fuel lines, and tank and stabilizes fuel for up to one year, thereby successfully averting any fuel-related problems. One ounce of Quickstor treats five gallons of fuel, so a 12-ounce bottle treats 60 gallons.

What is a transom on a Mercury outboard?

The transom on a Mercury outboard is the flat area at the back of the boat where the engine is mounted.

What are some common issues with Mercury outboard transoms?

Some common issues with Mercury outboard transoms include cracks, rot, and water infiltration.

What does Mercury outboard exhaust relief mean?

Mercury outboard exhaust relief refers to a feature designed to prevent backpressure buildup in the outboard engine's exhaust system. The exhaust relief system allows the engine to expel exhaust gases more efficiently, particularly at low speeds or during periods of increased load on the engine.

When an outboard engine is running, the exhaust gases generated by the combustion process are expelled through the exhaust system. However, at low speeds or when the boat is heavily loaded, the exhaust gases can create a backpressure in the system, which can negatively impact engine performance and potentially cause damage.

The exhaust relief system, also known as the "exhaust relief hole" or "exhaust relief port," is a small opening located on the lower unit of the outboard engine. It provides an alternate path for the exhaust gases to escape directly into the water, bypassing the propeller. This helps alleviate the backpressure and allows the engine to operate more efficiently.

The exhaust relief system is particularly important in applications where the engine operates at low speeds, such as trolling or idling. It helps maintain optimal engine performance, prevents overheating, and reduces the risk of engine damage caused by excessive backpressure.

It's important to note that the exhaust relief system is a standard feature in most modern Mercury outboard engines. It is designed and calibrated by the manufacturer to ensure proper operation and performance. Regular maintenance and inspection of the exhaust relief system, as recommended by the manufacturer, will help ensure its continued functionality and prevent any potential issues.

How does a Mercury Verado transom saver work?

The Mercury Verado transom saver is a device designed to support and protect the outboard engine during transportation or periods of non-use. Here's how it works:

1. Construction: The transom saver consists of a sturdy metal or composite bar with adjustable brackets on each end. It is typically attached to the lower unit of the outboard engine and secured to the boat's transom.
2. Support and Alignment: The purpose of the transom saver is to provide additional support to the outboard engine, relieving stress on the transom while the boat is being transported or stored. It helps maintain proper alignment between the engine and the transom, preventing excessive movement or strain.
3. Adjustable Length: The transom saver is adjustable in length to accommodate different boat sizes and engine heights. It can be extended or retracted to achieve the desired fit and support.
4. Shock Absorption: Some transom savers may feature built-in shock-absorbing mechanisms, such as rubber or spring-loaded components. These elements help absorb road vibrations and impact shocks, further protecting the engine and transom from potential damage.
5. Easy Installation and Removal: The transom saver is typically easy to install and remove. It usually attaches to the lower unit using adjustable brackets or clips, and it can be secured to the transom using straps, hooks, or other fastening mechanisms. This allows for convenient installation before transport and removal when the boat is in use.

By using a transom saver, the weight of the outboard engine is properly supported and distributed, reducing stress on the transom and minimizing the risk of damage during transportation or storage. It is an effective accessory for maintaining the longevity and performance of Mercury Verado outboard engines.

How does the exhaust system work on a Mercury outboard? What cools exhaust on Mercury outboards?

The exhaust cooling system on Mercury outboard engines uses a combination of water and air to cool the exhaust gases. Here's how it works:

1. Water Circulation: When the engine is running, water is drawn into the water intake on the lower unit of the outboard. This water is then circulated through the cooling passages inside the engine block to absorb heat from the internal components, including the exhaust passages.
2. Exhaust Passage: As the exhaust gases are expelled from the combustion chamber, they flow through dedicated exhaust passages within the engine. These passages are designed to route the exhaust gases towards the lower unit.
3. Water Injection: As the exhaust gases exit the engine, they pass through a water jacket surrounding the exhaust passages. Water from the water pump is injected into this jacket, mixing with the hot exhaust gases.
4. Cooling Effect: The injected water rapidly absorbs the heat from the exhaust gases, cooling them down. This process helps to prevent excessive temperatures in the exhaust system and protects the surrounding components from damage.
5. Water Discharge: The cooled exhaust gases, now mixed with water, exit the engine and are discharged through the exhaust ports on the lower unit. The water and exhaust mixture then exit the outboard through the propeller hub or via a dedicated exhaust outlet.

By utilizing this combination of water injection and circulation, the exhaust cooling system effectively cools the exhaust gases and prevents overheating. It is an important aspect of maintaining optimal engine performance and longevity in Mercury outboard engines.

Is my Mercury transom serial number located in the owner's manual?

No, the transom serial number of your Mercury outboard engine is not typically located in the owner's manual. The owner's manual generally provides information about the operation, maintenance, and troubleshooting of the engine but may not include specific details about the transom serial number.

The transom serial number, also known as the serial number plate or identification plate, is usually located on the transom bracket of the outboard engine. It is a metal plate or sticker that displays important information about the engine, such as the model number, serial number, and manufacturing date.

To locate the transom serial number, you can check the following areas on the engine:

1. Transom Bracket: Look for the serial number plate or sticker attached to the transom bracket. It is typically located on the starboard (right) side of the bracket.
2. Mid-Section: In some cases, the transom serial number may be located on the mid-section of the engine. Check the sides or rear of the mid-section for any identification plates or stickers.
3. Owner's Information Packet: While the owner's manual may not include the transom serial number, the owner's information packet provided by Mercury may contain a separate document or card with the serial number recorded for your reference.

If you are unable to locate the transom serial number on your Mercury outboard engine, it is recommended to consult the engine's manual or contact a Mercury authorized dealer for assistance. They can provide guidance on where to find the serial number specific to your engine model.

Where can I learn more about Mercury Engine Parts and Maintenance?

PartsVu understands that boaters want to learn how to perform their own Mercury outboard maintenance. From maintaining your Mercury outboard, Mercury sterndrive, and MerCruiser engines, there’s always something new to learn and save money. That’s why PartsVu offers our comprehensive blog, The PartsVu Xchange. 

Read up on the latest developments in boating, as well as search for everything you need to know about Mercury engine maintenance.

To get you off to a good start, these are some of the most important articles on Mercury Marine Engine Fuel & Oil System Components and more:

• Transom Saver, Outboard Motor Support - PartsVu
• Selecting & Installing M-Y Wedge Transom Supports
• Mercury Marine Outboard vs. MerCruiser Sterndrive Engines
• How to Select the Right Mercury Outboard Parts

What are the signs of a Mercury outboard clogged exhaust?

A clogged exhaust in a Mercury outboard engine can lead to various symptoms that indicate a potential issue. Some signs to watch for include:

1. Reduced Power: One of the common indicators of a clogged exhaust is a significant loss of power in the engine. You may notice a decrease in acceleration or a general lack of performance.
2. Overheating: A clogged exhaust can disrupt the proper flow of cooling water through the engine, leading to overheating. If you observe the engine temperature rising quickly or notice warning alarms related to high temperature, it could be a sign of a clogged exhaust.
3. Excessive Smoke: A clogged exhaust can cause the engine to produce excessive smoke, usually with a darker or thicker appearance. This smoke may be more noticeable during startup or while running at higher RPMs.
4. Increased Fuel Consumption: When the exhaust is partially blocked, the engine may struggle to expel exhaust gases efficiently. This inefficiency can result in increased fuel consumption, as the engine works harder to compensate for the restricted exhaust flow.
5. Rough Running or Stalling: A clogged exhaust can disrupt the engine's normal combustion process, leading to rough idling, misfiring, or even engine stalling. These symptoms may occur intermittently or persistently.

If you suspect a clogged exhaust in your Mercury outboard engine, it is crucial to address the issue promptly. Clogged exhausts can result from various factors, such as debris, carbon buildup, or damaged components. Consult with a qualified marine mechanic or technician to diagnose the problem accurately and perform the necessary repairs or maintenance to restore proper exhaust flow.

How do you know if your Mercury outboard transom needs to be replaced?

Signs that your Mercury outboard transom may need to be replaced include cracks, soft spots, and water infiltration.

What are the benefits of upgrading to a high-performance Mercury outboard exhaust system?

Upgrading to a high-performance Mercury outboard exhaust system can increase horsepower, improve fuel efficiency, and reduce engine noise.

Can I replace my Mercury outboard exhaust system myself?

While it is possible to replace your Mercury outboard exhaust system yourself, it is recommended that you have a certified mechanic perform the installation to ensure that it is done correctly.

What is the purpose of a Mercury outboard exhaust manifold?

The exhaust manifold on a Mercury outboard directs exhaust gases away from the engine and into the water, reducing emissions and increasing engine performance.

How often should you inspect your Mercury outboard exhaust system?

It is recommended that you inspect your Mercury outboard exhaust system at least once per year, and more frequently if you frequently use your boat in saltwater or dirty water conditions.

Can using aftermarket exhaust parts void my Mercury outboard warranty?

It is possible that using aftermarket exhaust parts could void your Mercury outboard warranty. It is important to check with your Mercury dealer or manufacturer before making any modifications to your engine.

What are the benefits of using a Mercury outboard exhaust extension?

Using a Mercury outboard exhaust extension can offer several benefits for boaters. Here are some advantages of using an exhaust extension:

1. Reduced Noise and Fumes: An exhaust extension can help redirect the exhaust gases and noise away from the boat and occupants. By extending the exhaust outlet, the engine noise and fumes are moved farther behind the boat, making for a quieter and more comfortable boating experience.
2. Improved Air Quality: Redirecting the exhaust gases away from the boat helps to improve air quality on board. Instead of breathing in the fumes emitted by the outboard engine, the exhaust extension directs them away from the boat, reducing the exposure to harmful emissions.
3. Minimized Water Spray: In rough water conditions, the exhaust extension can help minimize water spray coming into contact with the exhaust outlet. This can prevent water from entering the exhaust system and potentially causing damage to the engine.
4. Enhanced Performance: In certain boating applications, such as fishing or shallow water navigation, where stealth and maneuverability are important, an exhaust extension can help improve performance. By redirecting the exhaust gases away from the boat, it reduces disturbances in the water and minimizes the risk of spooking fish or encountering shallow areas.
5. Compliance with Regulations: Some boating areas or water bodies have specific regulations regarding exhaust emissions and noise levels. Using an exhaust extension can help ensure compliance with these regulations by effectively redirecting the exhaust and reducing noise emissions.

What is a transom exhaust and how does it work on a Mercury outboard engine?

A transom exhaust is a type of exhaust system commonly used in Mercury outboard engines. The exhaust gases exit the engine through the transom, which is the stern or back of the boat. This type of exhaust system is efficient and reduces the risk of backflow or water ingestion, which can damage the engine.

There is Mercury outboard oil leaking from exhaust - what does this mean?

If you notice oil leaking from the exhaust of your Mercury outboard, it could indicate a potential issue that requires attention. Oil leaking from the exhaust is not a normal occurrence and may be a symptom of an underlying problem. Here are a few possible causes and their implications:

1. Engine Oil Leakage: If the oil is coming directly from the exhaust, it suggests that engine oil is finding its way into the combustion chamber and being burned along with the fuel. This can be caused by worn piston rings, valve stem seals, or other internal engine issues. It's important to address this problem promptly as excessive oil consumption can lead to engine damage.
2. Incorrect Oil-to-Gas Mixture: If you have a two-stroke M