Marine exhaust systems are an important and often neglected engine of a ship. Most ships have a system of "wet" exhaust. The outlet for the exhaust gases from the exhaust manifold - the salt water is injected into the column. This mixture of gas and water is then passed through a series of curves to it from the boat, preferably in the back.
Exhaust fumes mixed with salt water to create a highly corrosive compound. This is why exhaust systems are often non-corrosivecomponents such as nitrile rubber reinforced hose (brown - not green - stripe), galvanized steel, fiberglass or plastic. The purpose of these components, which vary in size and shape depending on the engine size and layout of the engine room, is to prevent hydraulicing of the engine. This is caused when an engine has filled with salt water which has entered via the exhaust and can cause extensive damage if left for more than two hours. Water enters the exhaust from wave action at stern and poor Drain design. In some sea conditions, such as by sea, the water can again be forced to exhaust when the engine is not running. Drains poorly designed, that water will flow back and fill the waterlock / muffler box then the hose in the exhaust manifold, exhaust valves and combustion chamber. With the engine full of water can not compress the engine crank over, it is not like water.
Exhaust System
You will know that your engine is if you do not turn around hydrauliced -generally after a long sailing period - and you have removed the starter motor and ensured it works. To remove water from inside the combustion chambers, first remove all injectors, crank engine over to blow water out, refit injectors, bleed injector lines, and start. Then leave motor running until exhaust sorted out.
Check to see that the riser is not coked up or corroded - a common problem. To check the exhaust riser remove the exhaust hose from the riser (often a difficult procedure) and look up the pipe to see if it is restricted by exhaust/salt build up. If build up is excessive the riser will have to be removed to check the engine end of the pipe. Coke can be scraped out to provide a short term fix although often the riser will have to be replaced. There are aftermarket systems which vary in quality. Make sure you fit the right design for the application.
Ensure your water-lock is low enough and big enough to hold all the water in exhaust system. Is there a gooseneck or central vertical loop in the exhaust hose at the transom exit? Is there a siphon break and is it functioning properly - no leaking valves?
Exhaust gas is poisonous and can cause sea sickness and headaches. Replace any faulty parts immediately. Use double hose clamps on each joint or, preferably, super clamps, bolt style, and exhaust cement if need be. Hot sections should be lagged with fiberglass tape to prevent burns.
Beware of asbestos lagging. Many older vessels and Marine engine installations had exhaust systems that were lagged with asbestos tape and rope. Asbestos was common in older boats noise.
Understanding A Marine Exhaust System
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