1969 Evinrude 40 HP Big Twin, Big Twin Electric Lark Service Manual 4596, Page 44Get this manual
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dowel pinA roller bearing at the bottom journal absorbs the radial and vertical thrust loads of the crankshaftCOOLING SYSTEM Water for engine cooling is supplied by two-stage pump containing rubber impellerAt low speeds, the pump operates as full displacement pumpAt higher speeds, the impeller blades bend back under the increased water pressure and the pump becomes centrifugal action pumpSee Figures 5-3A5- 3BTHERMOSTAT OPERATION The thermostat housing contains the pressure valve and spring, and the thermostatThe circulation of water through the cooling system by the water pump and the ratio of coolant discharge to intake is controlled by the balanced action between the pressure control valve and the thermostatSee Figure 5-4When the power head and cooling system temperatures reach 145 the thermostat opens, allowing heated water to pass through the water dischargeThe drop in cooling system pressure caused by the opening of the thermostat causes the pressure valve to close, preventing the cooling system water from being recirculated through the water pump and causing fresh water to be drawn through the water intakeThis action provides perfect water jacket temperatures in any water and any weatherC LI ND LOC K