VETUS marine exhaust systems are based on ‘wet’ systems. This is the process in which the cooling water is injected into the exhaust line.  This reduces the gas temperature along with reducing fumes.

With the engine being at the heart of any vessel, it is important to fit the correct engine exhaust system. This will reduce maintenance costs, increase performance and is also safer for the crew.

The system is often hidden but plays a vital role in making sure the crew are not exposed to toxic exhaust gases by transporting these safely away. It also transports raw water or sea water and protects the engine against water ingress.

The main components of the exhaust system are the mixing elbow, the waterlock and the gooseneck. Additional components are an exhaust alarm and an air vent. There are also lesser-known options such as a gas water separator for a very quiet installation.

It starts with the intake grate/inlet valve

The first part of a well-designed wet marine exhaust system is the intake grate which only allows the engine cooling water to be sucked in when the engine is running and will filter the water to make sure items like plastic bags are not sucked up.

The mixing elbow is where hot exhaust gases of up to 400 degrees Celsius are mixed with cold cooling water with temperatures dropping to around 40 or 50 degrees Celsius.

A flexible hose supplies cooling water to the impeller pump which moves the water through the heat exchanger where it is then forced into the mixing elbow. When installing the system, the hose should be kept as straight down as possible from the mixing elbow to the water lock to ensure a good mix of cold water and hot gases, if this is not possible, a swirler or mixer can be fitted.

Prevention of backflow

A waterlock, which fits onto the hose, is used to pump the mix of exhaust gases and cooling water overboard. A VETUS waterlock of the correct capacity will prevent water backflowing into the engine. When the engine is stopped, the waterlock will collect the water in the system, preventing it from damaging the engine.

VETUS designs waterlocks to withstand temperatures found in exhaust systems and has developed special plastics to use instead of stainless-steel.

We prefer to use specialist materials for our waterlocks as it has a longer lifespan than stainless-steel. The drawbacks of stainless steel are that it needs oxygen to form a protective layer for longevity. This oxygen is not found in an exhaust system because the engine uses it to burn fuel. In addition, the acidic exhaust fumes will start to attack and corrode the stainless-steel.

Other features of our waterlocks include noise reduction capabilities and a drain plug for winter storage.

There are three steps to follow when choosing the correct waterlock.

  1. Check the exhaust diameter of the mixing elbow
  2. Check how much room is available and how the hoses in and out of the waterlock are connected
  3. Calculate how big the waterlock should be so that it is able to contain all the water that is in the system at engine shut down. The more hose there is, the more water there will be in the system.

A gooseneck provides a high point

The gooseneck will provide additional protection to the system, particularly against waves hitting the back of the boat. The gooseneck will create a high point in the exhaust system so water cannot enter the exhaust system. This high-point should be 45cm but don’t go over 150cm as this will create excessive back pressure in the system. The gooseneck can be formed using a flexible hose or for easier installation, VETUS has developed a gooseneck with a rotating top or bottom.

For a quieter system, a gas water separator can be installed to separate the exhaust gases from the water. The water will then drain from the bottom and the exhaust gases will exit quietly out of a top fitting. On faster boats with a continuous downslope from the engine to the transom, a muffler can be fitted to dampen the exhaust noise.

The final part of the exhaust system is the transom connection which is typically fitted with a non-return valve so any waves are blocked before they can enter the system.

Additional components for marine exhaust systems

All VETUS diesel engines are equipped with an exhaust alarm which can also be retrofitted to a wet exhaust system. The alarm has a small sensor. This sensor can be installed in the muffler, the waterlock, or even screwed into the hose. It provides an early warning of problems with the cooling water flow and rising engine temperature. Usually, the engine temperature will rise before your exhaust temperature. If the engine temperature does rise, it can cause the engine to seize up, leading to significant damage.

When the cooling water injection point is less than 15cm above the waterline, the cooling system can siphon water through the intake when the engine is turned off. VETUS air vents will prevent the water siphoning into the exhaust system and into the engine itself. The air vent need to be installed at least 40cm above the waterline.

Developed in-house

At VETUS, we have a variety of wet exhaust systems for different boats depending on the look that you want to achieve. Our range is developed in-house which gives us the opportunity to pay extra attention to safety and reliability, giving you the ultimate carefree boating experience. An extra benefit from our entire exhaust range is that it is manufactured using synthetic composite and reinforced materials, making them more durable and longer lasting. In fact, we are happy to say a VETUS marine exhaust system will last a boat’s lifetime. We hope you enjoy your time on the water.

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