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Exhaust System design

The engine is equipped for a "wet marine" exhaust system. That is, the waste raw water is injected into the Exhaust Elbow and sprayed into the hot exhaust gases to cool them. The cooled waste water and exhaust gas mix is then disposed of through a marine "percolating" type muffler and a 1½" I.D. marine grade, wire reinforced exhaust hose. The rear of the Enclosure has a hole for the exhaust hose to pass through so it can be secured to the Exhaust Elbow on the engine.
exhaust inlet

Percolating mufflers are available from several manufacturers with different brand names. Aqualift, Water Lock, Water Lift, etc., are just a few. They all operate on the same principal. The device is divided into two sections. A large surface area on the input side, and a small surface area on the outlet side. A vertical baffle divides the two sections from the top to just above the bottom. The mixed water and exhaust gas is fed into the top or side of the percolator. The water falls to the bottom of the percolator and the gas escapes around the bottom of the baffle and through the outlet. As the water level rises, the opening to the outlet side is blocked and the gas is trapped in the input side. Exhaust gas pressure (back pressure) increases and applies a force to the large surface area of the water. Ultimately this force reaches sufficient strength to "lift" some of the water up the outlet side to the outlet port. This "percolated" water proceeds upward to the high point of the exhaust system, crosses over the high point, then gravity flows to the exhaust thru hull and overboard. There are several critical points to consider.
Typical Installation
In a typical installation, that is, one in which the generator is located above the waterline, the Exhaust Elbow on the engine must be at least 12" above the waterline, in all conditions.
Percolator Inlet
The inlet to the percolator muffler must always be 4" or more below the Exhaust Elbow outlet of the engine, including the effects of pitch and roll on the vessel. The connection should be within a reasonable horizontal distance, never loop up and down, but always proceed in a steady downward direction.
Percolator Outlet
The outlet of the percolator should be connected to 1½" I.D., wire reinforced, marine grade exhaust hose. The hose should run in a vertical or near vertical direction until it reaches at least 10" above the vessel waterline. At that point it can be curved over and should continue in a downward direction to the exhaust thru hull. The horizontal distance from the top of the curve to the thru hull has no limit on length; however, once the hose starts its downward direction it must never loop up and down. If in doubt, call us for consultation.
When a typical marine exhaust system is installed with the thru hull mounted above the vessel's waterline, it is not unusual to hear a "whooshing" noise on the outside of the vessel near the exhaust outlet. This can be reduced, or in some cases eliminated, with the installation of one or two inline exhaust silencers. Be sure to select a silencer that does not restrict the exhaust flow and create "back pressure."

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