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General Engine Checks by Joe Reeves

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  • General Engine Checks by Joe Reeves

    (General Engine Checks)
    (J. Reeves)

    First, check the compression. It should be approx 100+ psi and even on all cylinders.

    Next, with the s/plugs removed, check the spark. It should jump a 7/16" gap with a strong blue flame on all cylinders. (The s/plugs must be removed in order to obtain the highest rpm available). On engines 1972 and older, and engines without solid state ignition, set the tester gap to 1/4". (You neglected to mention the year of the engine!)

    - - - - -
    (Magneto Capacitance Discharge Coils)
    Check the continuity of the ignition coils. Remove the primary orange wire from whatever it's connected to. It may be connected to a powerpack screw type terminal, a rubber plug connector, or it may simply plug onto a small boss terminal of the coil itself.

    Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground of the coil or the powerhead itself if the coil is still installed.

    Then touch (still with the red lead) the orange wire if it's attached to the coil, or if it's not attached, touch the primary stud of the coil. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire. Poor or no continuity of a coil is one reason for s/plug fouling.

    - - - - -
    (Battery Capacitance Discharge Coils - Continunity Test)
    (Joe Reeves)
    Remove the primary wire the screw type terminal. Remove the coil and unscrew the HT wire from the distributor cap.

    Connect the black lead of a ohm meter to the HT wire, then with the red ohm meter lead, touch the ground wire of the coil.

    Then touch (still with the red lead) the wire that normally attaches to the powerpack output lead. You should get a reading on both touches (contacts). If not, check the HT wire by unscrewing it from the coil. After removing the wire, the check can be repeated using the internal threaded prong within the coil instead of the HT wire. Poor or no continuity of a coil is one reason for erratic or no ignition and/or s/plug fouling.

    - - - - -
    NOTE..... For the older magneto ignition coils, the continuity check would be as follows:

    Checking the continuity of the ignition coils....... Have the ohm meter set to High Ohms.

    Remove the primary wire from points. Remove the coil ground wire. You do not want either of these wires touching anything.
    Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground wire of the coil.

    Then touch (still with the red lead) the primary wire. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire.

    If there is no continuity between the secondary circuit (spark plug) wire and the primary or ground, remove the coil from the armature plate, then check the continuity directly between the prong within the coil (prong that the plug wire connects to) and the primary and ground. Poor or no continuity of a coil (or plug wire) is one reason for weak spark, s/plug fouling, or no spark.
    - - - - -

    When removing the spark plugs, make a note of which s/plug came from what cylinder. They should all look alike, but if not, that difference should lead a mechanic in a certain direction.

    Remove the spark plugs, then insert a screwdriver or some such object into the cylinder, and have it rest on top of the piston. Do not apply pressure to the screwdriver yet. You simply want to know where the piston is. Now, turn the flywheel by hand and get the piston to come up to dead top center, then drag it down about 1" by turning the flywheel. Now, hold the flywheel tightly and apply pressure to that screwdriver or whatever object you're using. If you can move that piston without moving the flywheel, that indicates that there is play in either the wrist pin area or at the crankshaft to connecting rod area.

    If the engine has been sitting for any length of time (a couple months or more), there's a very good possibility that the carburetor(s) are somewhat fouled/clogged/gummed. If so, they'll require removing, cleaning, and rebuilding.

    Remove the carburetor face plate. Observe the carburetor(s) while you pump the fuel primer bulb. If fuel flows out of the carburetor(s), they will require removing, cleaning, and rebuilding.

    (With Engine Not Running) Check that the throttle plate butterflies are opening full (horizontal) when full throttle is applied. Also check to see that the timer base under the flywheel is advancing to the full spark advance point, up against the rubber cap of the spark advance stop screw.

    Check, while under way, that the engine engages both forward and reverse properly, and that the engine does not jump out of forward gear at a high rpm.

    When running the engine, pulling each s/plug boot terminal off of the s/plugs should result in a even rpm drop throughout.

    stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store



    ---
    ReevesJ32@aol.com

    30+ Years With OMC


    "JUST KEEP ON, KEEPING ON"©
    "Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, chocolate in one hand, martini in the other, body thoroughly used up, totally worn out and screaming "WOO HOO what a ride!"
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