1969 Evinrude 40 HP Big Twin, Big Twin Electric Lark Service Manual 4596, Page 64Get this manual
DESCRIPTION RUBBER MOUNTS AND SEALS There are two exhaust housings: an inner housing or exhaust tube; and an outer housing enclosed by combination of front and rear cover assembliesThe outer exhaust housing, which carries the power head, "floats" inside the front and rear covers on six rubber mounts and the exhaust tube seal ringIn this way, all power head and driveshaft vibrations are completely isolated and are prevented from being transmitted to the stern bracket and the boat transomIn addition, the rubber seal ring positions the outer exhaust housing within the rear exhaust cover and also prevents water and exhaust gases from rising above this pointSee Figure 6-1EXHAUST RELIEF Normally, exhaust gases are conducted down through the inner exhaust tube and out through the underwater exhaust outletHowever, in starting, water in the underwater outlet creates back pressureThis can cause hard startingExhaust relief is provided by an outlet in the water discharge passage above the waterlineSince no water is discharged until after the motor is started, the exhaust gases will initially be discharged through the water discharge outletSee Figure 6-2