When installing bolts, you can lubricate the threads and underside of the head with 2-stroke oil. You can also snug the bolts in a box pattern, starting in the center.
The cylinder head, exhaust plate, and crankcase bolts on the Mercury 2.5 Liter 200 HP should torqued in a series of passes, increasing in torque from just tight to final torque. The pattern is circular, starting in the center and moving outward toward each end.
If the head bolts aren't torqued properly, the head gasket may fail. This can lead to several issues, including Loss of compression, Mixing of oil and coolant, Exhaust gases in the cooling channels or oil ways, Cylinder head erosion, and Cylinder head overheating and warping.
Here are some steps to check the torq on your cylinder head bolts on a Mercury 2-stroke outboard motor block:
Run the outboard for 30 minutes to an hour to warm the block
Let the block cool for two hours
When the engine is cold, follow the torque sequence and tighten each bolt individually
Loosen the bolt a quarter turn and retorque it to 30 ft-lbs.
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