38992 Mercruiser BUSHING, TEMPERATURE SWITCH

Valve Lash Setting
The valve lash setting is for a cold engine.Valve lash settingInlet valve ... 0.2 0.05 mm (0.008 0.0020 inch)Exhaust valve ... 0.2 0.05 mm (0.008 0.0020 inch)Valve Lash Adjustment
If the valve lash requires adjustment several times in a short time period, excessive wear exists in a different part of the engine. Repair the problem to prevent more damage to the engine.Not enough valve lash can be the cause of rapid wear of the camshaft and valve lifters. Not enough valve lash can indicate that the seats for the valves are worn.Valves become worn due to the following causes:
Incorrect operation of fuel injectors
Excessive dirt and oil are present on the filters for the inlet air.
Incorrect fuel settings on the fuel injection pump.
The load capacity of the engine is frequently exceeded.Too much valve lash can cause broken valve stems, springs, and spring retainers. Too much valve lash can be an indication of the following problems:
Worn camshaft and valve lifters
Worn rocker arms
Bent pushrods
Broken socket on the upper end of a pushrod
Loose adjustment screw for the valve lashIf the camshaft and valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.The valve lash is measured between the top of the valve stem and the rocker arm lever.Note: No. 1 cylinder is at the front of the engine.Remove the valve mechanism cover. Refer to Disassembly and Assembly, Valve Mechanism Cover - Remove and Install for the correct procedure.Perform the following procedures to adjust the valve lash:Note: When these procedures are performed, the front housing must be installed.
Illustration 1 g01107989
Setting the valve lash
(1) Feeler gauge
(2) Adjustment screw
Accidental engine starting can cause injury or death to personnel.To prevent accidental engine starting, turn the ignition switch to the OFF position and place a do not operate tag at the ignition switch location.
Valve Lash Adjustment for Three Cylinder Engines
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 1 cylinder has started to open and the exhaust valve of the No. 1 cylinder has not completely closed, check the valve lash of the inlet valve of No. 2 cylinder and the exhaust valve of No. 3 cylinder. If necessary, adjust the valve lash.
Loosen the valve adjustment screw locknut that is on adjustment screw (2).
Place the appropriate feeler gauge (1) between the rocker arm and the valve. Turn adjustment screw (2) while the valve adjustment screw locknut is being held from turning. Adjust the valve lash until the correct specification is achieved.
After each adjustment, tighten the valve adjustment screw locknut while adjustment screw (2) is being held from turning.
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 2 cylinder has started to open and the exhaust valve of the No. 2 cylinder has not completely closed, check the valve lash of the inlet valve for No. 3 cylinder and the exhaust valve for No. 1 cylinder.If adjustment is necessary, refer to Steps 1a, 1b, and 1c above.
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 3 cylinder has started to open and the exhaust valve of the No. 3 cylinder has not completely closed, check the valve lash of the inlet valve for No. 1 cylinder and the exhaust valve for No. 2 cylinder.If adjustment is necessary, refer to Steps 1a, 1b, and 1c above.
Install the valve mechanism cover. Refer to Disassembly and Assembly, Valve Mechanism Cover - Remove and Install for the correct procedure.Note: Ensure that a new gasket is installed when the valve mechanism cover is installed.Valve Lash Adjustment for Four Cylinder Engines
Illustration 2 g03340755
A typical example of the crankshaft pulley and front housing
Illustration 3 g03340756
Top center markings for the Crankshaft pulley
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 4 cylinder has started to open and the exhaust valve of the No. 4 cylinder has not closed, ensure the "Top" mark (3) on the timing case aligns with "Single dot" (4) on the crankshaft pulley. Check the valve lash of the inlet valve and the exhaust valve of the No. 1 cylinder. Check the valve lash of the inlet valve of the No. 2 cylinder. Check the valve lash of the exhaust valve of the No. 3 cylinder. If necessary, adjust.Note: The "Single dot" (4) on the crankshaft pulley is the reference point for the top center position of No. 1 cylinder.
Loosen the valve adjustment screw locknut that is on adjustment screw (2).
Place the appropriate feeler gauge (1) between the rocker arm and the valve. Turn adjustment screw (2) while the valve adjustment screw locknut is being held from turning. Adjust the valve lash until the correct specification is achieved.
After each adjustment, tighten the valve adjustment screw locknut while adjustment screw (2) is being held from turning.
Rotate the crankshaft in a clockwise direction 360°. When the inlet valve of the No. 1 cylinder has started to open and the exhaust valve of the No. 1 cylinder has not closed, ensure the "Top" mark (3) on the timing case aligns with "Single dot" (4) on the crankshaft pulley. Check the valve lash of the exhaust valve of the No. 2 cylinder. Check the valve lash of the inlet valve of the No. 3 cylinder. Check the valve lash of the inlet valve and the exhaust valve of the No. 4 cylinder. If necessary, adjust.If adjustment is necessary, refer to Steps 1a,1b, and 1c above.
Install the valve mechanism cover. Refer to Disassembly and Assembly, Valve Mechanism Cover - Remove and Install for the correct procedure.Note: Ensure that a new gasket is installed when the valve mechanism cover is installed.