GENERAL INFORMATION
90-826883R2 JUNE 1998 Page 1C-9
8. Place a block of wood between gear case and propeller and tighten propeller nut.
Compression Check
1. Remove spark plugs.
2. Install compression gauge in spark plug hole.
3. Hold throttle plate at W.O.T.
4. Crank the engine over until the compression reading peaks on the gauge. Record the
reading.
5. Check and record compression of each cylinder. The highest and lowest reading
recorded should not differ by more than 15% (see example chart below). A reading
below 120 psi might indicate a total engine wear problem.
Example of compression test differences
Maximum (psi)
Minimum (psi)
180 162
150 127.5
6. Compression check is important because an engine with low or uneven compression
cannot be tuned successfully to give peak performance. It is essential, therefore, that
improper compression be corrected before proceeding with an engine tuneup.
7. Cylinder scoring: If powerhead shows any indication of overheating, such as discol-
ored or scorched paint, visually inspect cylinders for scoring or other damage as out-
lined in Section 4 “Powerhead.”
To Next Page
Loading...
Need help?
General
