Marine exhaust systems are an important and often overlooked part of a marine engine. Most vessels have a “wet” exhaust system. Salt water is injected on the rise – the exhaust outlet of the exhaust manifold. This mixture of exhaust gases and water is passed through a series of bends until it exits the boat, preferably in the stern.
The exhaust gas mixes with seawater to create a highly corrosive compound. This is why exhaust systems are commonly made using non-corrosive components such as nitrile rubber tube reinforced (brown – not green – banda), galvanized steel, fiberglass or plastic. The purpose of these components, which vary in size and shape, depending on engine size and design of the engine room, is to prevent engine hydraulicing. This is caused when an engine is filled with salt water that has entered through the exhaust and can cause extensive damage if left for more than two hours. The water enters the exhaust pipe of the action of waves on the stern exhaust design and the poor. Under certain conditions the sea, like a sea below, the water can be forced back up the exhaust pipe when the engine is not running. Poorly designed exhausts allow water to flow back and fill the waterproof box / silencer then up the hose to the exhaust manifold through the exhaust valves and the combustion chamber. With the engine full of water the engine can not handle on how it is and can not compress water.
You’ll know your engine is turned hydraulic unless more – usually after a long sailing period – and removed the starter and made sure it works. To remove water from inside the combustion chambers, first remove all injectors, crank the engine to blow water injectors reassemble, bleed the injection lines and outset. Then leave the motor running until exhaust resolved.
Check that the elevator is not coked up or corroded – a common problem. To check the rising exhaust outlet pipe to remove the riser board (often a difficult process) and look to see if the pipe is restricted by the exhaust / salt build up. If the amount is excessive build shall be removed to check the motor end of the pipe. Coca-Cola can be scraped to provide a short term solution, but often the elevator must be replaced. There are aftermarket systems which vary in quality. Make sure you place the right design for the application.
Make sure the water block is low enough and large enough to hold all the water in the exhaust system. Is there a link gooseneck or central vertical exhaust pipe at the exit of the mirror? Is there a siphon break and is working properly – no exhaust valves?
Exhaust fumes are poisonous and can cause dizziness and headaches. Replace defective parts immediately. Use double hose clamps clamps on each superset or, preferably, in the style of the post and cement escape if necessary. Sections should be with hot fiberglass tape left to avoid burns.
Beware of asbestos lagging. Many older vessels and marine engine installations had exhaust systems that will keep the tape and rope asbestos. Asbestos insulation was also common in older boats.