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