OMC Stern Drives And Motors 1964-1986 Repair Manual., Page 26Get this manual
2 TUNING 2-1 INTRODUCTION
The efficiency, reliability, fuel economy and enjoyment you receive from the engine's performance all directly dependent on having tuned properlyThe importance of performing service work in the sequence detailed in this chapter cannot overemphasizedBefore making any adjustments, check the specifications in the AppendixDo not rely on your memoryBefore beginning tune any engine, check be sure the engine cylinders have satisfactory compressionAn engine with worn piston rings, burnt valves, blown gasket cannot be made perform properly how much and expense is spend on the tune-upPoor compression must corrected or the tune-up will not give the desired results2-2 TUNING
very important complete the ignition work before moving the fuel system because the ignition adjustments have so much on the carburetion
2-3 MECHANICAL TASKS
Check the drive belt least once year or during each tune-upReplace the belt if there is any evidence of crack or on the under surfaceIf is necessary to install new belt, be sure use only the size and type recommended by the engine manufacturerAdjust the belt tension by first loosening the brace and pivot bolts, and then pivoting