805733 Mercruiser SCREW, (.250-28 x 1.00)

Engine lubrication is accomplished by forced lubrication system using gear pump. The engine oil in the oil pan is drawn up through the oil strainer by the oil pump and force-fed to the oil filter and oil cooler to lubricate all parts.(1) Oil Pump The oil pump, of a gear pump type, is mounted in the rear bottom portion of the crankcase, driven by the crankshaft gear.An oil strainer is mounted at the suction port of the oil pump; an oil pipe at the delivery port.Since the oil pump is driven at speeds proportional to the engine's, the delivery pressure of the oil pump increases during starting in cold weather. A relief valve is built into the oil pump to protect the lubrication system from overpressure.(2) Oil Filter(a) Spin-on type The oil filter is a double oil filter consisting of a full-flow filter made integral with a bypass filter.The element is the spin-on type that is easy to replace. Engine oil passing through the full-flow filter is flows to the oil cooler. Engine oil passing through the upper filter (bypass filter) flows through the oil filter bracket mounting bolt hole to return to the oil pan.The oil filter bracket has the oil bypass alarm mounted whose bypass opens automatically to allow oil before filtering to flow to the oil cooler when the pressure difference across the element exceeds specified level. The oil bypass alarm has electrical contacts that are closed to turn on the warning lamp, warning the driver of clogged element when the valve is opened. As this oil filter is located at relatively high position, it is likely that oil flows down and the oil filter runs short of oil when the engine is stopped. In order to prevent backflow of oil, therefore, a check valve is provided. Also on the bypass side, a bypass check valve that opens only when oil pressure exceeding specified level acts is provided. By this arrangement, the oil level in the filter is always kept constant and quick lubrication of lubricating parts is ensured at time of engine start.(b) Element replaceable type The oil filter is a double oil filter consisting of a full-flow filter made integral with a bypass filter.Engine oil passing through the full-flow filter is flows to the oil cooler. Engine oil passing through the upper filter (bypass filter) flows through the oil filter bracket mounting bolt hole to return to the oil pan.The oil filter bracket has the oil bypass alarm mounted whose bypass opens automatically to allow oil before filtering to flow to the oil cooler when the pressure difference across the element exceeds specified level. The oil bypass alarm has electrical contacts that are closed to turn on the pilot lamp, warning the driver of clogged element when the valve is opened. As this oil filter is located at relatively high position, it is likely that oil flows down and the oil filter runs short of oil when the engine is stopped. At the inlet, therefore, a check valve that opens at very small pressure and center pipe are provided to keep the oil level in the filter constant, thereby ensuring quick lubrication of lubricating parts at time of engine start.(3) Oil Cooler The shell-and-plate type (multi-plate type) oil cooler is mounted in the coolant path on the left side of the crankcase.Engine oil forced through the oil filter is cooled or heated in the oil cooler element before it flows to the main oil gallery. When the oil viscosity is high at low temperatures or when the element has high resistance to flow because of clogging, the oil bypass valve installed at the oil cooler opens to allow engine oil to flow to the main gallery bypassing the oil cooler.(4) Regulator Valve The regulator valve is mounted at the lower portion of the injection pump on the left side of the crankcase. It regulates pressure of engine oil that flows through the oil filter and oil cooler into the main gallery.When oil pressure in the main gallery exceeds specified level the regulator valve opens to return part of engine oil to the oil pan.(5) Lubrication of All PartsThe engine oil routed to the main oil gallery lubricates all parts as described in the following.(a) Main bearing and connecting rod bearing The oil main gallery connects to the crankshaft main bearing through oil holes for lubrication of the main bearing. Part of engine oil that has lubricated the main bearing flows through the oil