1968 Evinrude Big Twin, Big Twin Electric, Lark 40 HP Outboards Service Manual, Page 57Get this manual
DESCRIPTION RUBBER MOUNTS AND SEALS There are two exhaust housings: an inner housing or exhaust tube; and an outer housing enclosed combination of front and rear cover assembliesouter exhaust housing, which carries the power head, "floats" inside the front and rear covers six rubber mounts and the exhaust tube seal ringIn this way, power head and driveshaft vibrations are completely isolated and are prevented from ing 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 6-1 RELIEF Normally, exhaust gases are cond.lcted down through the inner exhaust tube and out thr ough the underwater exhaust outletHowever, in starting, water in the underwater outlet creates back pressureThis cause hard startingExhaust relief is provided outlet in the water discharge passage above the waterlineSince water is discharged until after the motor is started, the exhaust gases will initially discharged through the water discharge outletSee Figure 6-2