![]() The fan blades spin to force air to flow in and out of cabin spaces. ![]() Powered ventilation systems use blowers to circulate air. These are far more common, especially in modern boats. The alternative to natural ventilation is powered. Diesel-powered inboards and sterndrives are also not subject to the ventilation requirement since diesel fumes are not explosive, but most still have systems to ventilate their engine compartments. These cowl vents increase airflow when the boat is in motion. Powered Ventilation System: All boats built later than July 31 st, 1982 with an inboard engine or with installed fuel tanks, must have a powered ventilation system (which consists of one or more exhaust blowers). Outboard-powered boats with permanent fuel tanks that are vented outside the boat are not required to have ventilation systems - unless they have a gas generator on board in an enclosed space. As well as posing health risks when inhaled, the fumes are also obviously very flammable and explosive. Without the right type of vents or accessories like blower fans, the buildup of fumes becomes dangerous. In most boats, there is always the risk, whether large or small, that gas fumes can build up. This latter requirement applies to virtually all gas-powered inboard and sterndrive boats. Every closed compartment containing a gas engine or gas tank must be ventilated by at least two ventilator ducts, and engine compartments containing a gas engine with a cranking motor must be ventilated by powered exhaust blowers operated from the instrument panel. If you move a few decades forward in time, the law was amended in 1982 to make a distinction between powered ventilation and natural ventilation. He can be reached via his website at first legal requirement for boat ventilation was as far back as April 1940 when, by law, all boats powered by gasoline required sufficient ventilation. He’s also an author, public speaker, and multiple award-winning journalist whose articles on seamanship, marine electronics, vessel maintenance and consumer reports appear regularly in numerous marine publications worldwide. Frank LanierĬaptain Frank Lanier is a SAMS® Accredited Marine Surveyor with more than 40 years of experience in the marine and diving industry. They can introduce Carbon monoxide (CO) into the vessel’s interior with deadly results. This lets the system be positively closed to prevent water entry from following seas during offshore voyages when the engine is not utilized.Īnother angle of a badly corroded manifold-to-riser joint.īecause labor is typically the biggest cost associated with doing this, most boat owners will forego testing and simply replace old manifolds and risers once pulled regardless of condition, particularly if the vessel is used in salt water.įinally, check the exhaust system with the engine off and while in operation because some leaks will only occur with the engine running.Īside from maintenance, finding and correcting exhaust leaks are also important from a safety standpoint. Some sailboat exhaust discharge installations may also feature a valve or seacock. ![]() Vessels with a transom exit exhaust should also have an exhaust valve, which is simply a rubber flapper valve that attaches to the outside of the exhaust, creating a one-way check valve to help prevent water (such as from wave action) from entering the exhaust and possibly the engine itself. Additionally, all hose connections should be made to a rigid component (pipe, muffler, exhaust outlet, etc.) hose to hose connections or joints should never be used. four times the inside diameter of the hose) should utilize wire reinforced hose. Hoses for example, should be labeled “marine wet exhaust” and be able to withstand heat, water weight, pressure, oil and acids.Īnything other than short hose runs (i.e. All materials used in the exhaust system should ideally be labeled as to their suitability. Maintenance TipsĪ great familiarization and maintenance strategy is to conduct an inspection of the exhaust system at regular intervals, such as part of a fall layup or spring commissioning routine. If this exhaust elbow looks like this on the outside, imagine how clogged the internal water passages are. Powered or Forced Ventilation: The USCG revised the regulations in 1980 to require powered ventilation systems on gasoline fueled inboard, inboard/outboard.
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