Mercury FourStroke 2.5, Руководство по обслуживанию, Страница: 34 / 205

General Information
90-8M0065421 NOVEMBER 2012 Page 1C-9
11. If the engine fails to start, determine if the cause is fuel, electrical, or mechanical. The engine should be run within two
hours after recovery from the water, or serious internal damage will occur. If unable to start the engine within two hours of
recovery, disassemble the engine and clean all parts. Apply oil as soon as possible.
Compression Check
1. Remove the spark plug.
2. Install the compression gauge in the spark plug hole.
3. Hold the throttle plate at WOT.
4. Pull on the recoil rope to crank the engine over until the compression reading peaks on the gauge. Record the reading.
5. A compression check is important because an engine with low compression cannot be tuned successfully to give peak
performance. It is essential, therefore, that improper compression be corrected before proceeding with an engine tune‑up.
6. Cylinder scoring: If powerhead shows any indication of overheating, such as discolored or scorched paint, visually inspect
cylinders for scoring or other damage as outlined in
Section 4
‑
Powerhead.
Cylinder Leakage Testing
NOTE: Cylinder leakage testing, along with compression testing, can help the mechanic pinpoint the source of a mechanical
failure by gauging the amount of leakage in an engine cylinder. Refer to the manufacturer's tester instructions for proper testing
procedures.
NOTE: Spark plug hole is a 14 mm diameter. Use Snap‑On Tool MT26J‑200 adapter (or equivalent) with valve core removed.
Cylinder Leakage Tester Snap‑On EEPV309A
1. Remove the spark plug.
2. Rotate the engine clockwise until resistance is felt.
3. Continue to rotate flywheel so the timing marks on the flywheel and cylinder block are in alignment. This will be the
compression stroke for the cylinder.
4. Complete the cylinder leak down test. Refer to the manufacturer's tester instructions for proper testing procedures.
Analysis
Due to standard engine tolerances and engine wear, no cylinder will maintain a 0% of leakage. Leakage greater than 15%
indicates excessive leakage.
If excessive leakage is present, first check that the piston is at top dead center of its compression stroke. Leakage will naturally
occur if the exhaust or intake valve is open.
To determine the cause of high percentage leaks, you must locate where the air is escaping from. Listen for air escaping
through the intake, adjacent spark plug holes, exhaust pipe, and crankcase oil fill plug. Use the following table to aid in locating
the source of cylinder leakage.
Air Escaping from Possible Location
Air induction Intake valve
Exhaust system Exhaust valve
Oil fill plug Piston/rings
Tell‑tale hose Head gasket
Painting Procedures
!
WARNING
Continuous exposure to airborne particles such as chemical vapors, dust, or spray can cause serious injury or death. Ensure
that the work area is properly ventilated and wear protective eyeware, clothing, and respirators.
Propellers
1. Sand the entire area to be painted with 3M 120 Regalite Polycut or coarse Scotch‑Brite disc or belts.
2. Feather edges of all broken paint edges. Try not to sand through the primer.
3. Clean the surface to be painted using PPG Industries DX330 Wax and Grease Remover or equivalent (Xylene or M.E.K.).
4. If bare metal has been exposed, use Mercury/Quicksilver Light Gray Primer.
5. Allow a minimum of one hour dry time and no more than one week before applying the finish coat.
6. Apply the finish coat using Mercury/Quicksilver EDP Propeller Black.