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How To Diagnose Outboard Starting Problems

Boats & Engines > How To Diagnose Outboard Starting Problems


Engine problems are a fact of life for boaters. They never come at a convenient time. A family at the lake had spent half the day trying to get their boat operating when one of the teenage sons impatiently asked, “When are we going to go boating?” The mother wisely replied, "Son, we ARE boating."

Diagnosing starting problems on your outboard is a skill that comes with experience. Whether you are a dock side / parking lot mechanic who can dig in to do the repair on your own, or a novice who just wants to gain a better understanding of what is happening with your engine, here are a few tips from one of our experienced iboats Boating Forums members, JB.

Note: Remember to make sure you actually have fuel in your gas tank before you proceed, otherwise you might find yourself the topic of a “Stupid Human Boating Tricks” entry in another part of our Forums.

Outboard Won’t Start:

    1. Electric start:

    • Does the starter engage and rotate the flywheel at a good (normal) speed? If yes, go to 2.
    • Does starter spin, but Bendix gear (small gear on starter shaft) does not engage the flywheel? Lubricate Bendix spiral shaft.
    • Does the solenoid click? * If yes, measure voltage at the starter terminal to battery ground with starter engaged.
      • If 12 V, repair or replace starter.
      • If less than 9V measure voltage at large solenoid input terminal (from battery).
      • If less than 9V, go to 3.
      • If 12V, replace solenoid.
    • Solenoid does not click when key is turned to start. Measure voltage at small solenoid terminal.
      • 0 volts? Troubleshoot kill switch (lanyard connected?), battery, starter switch and neutral start switch in controller.
      • 2 volts? Replace solenoid.

    2. Flywheel rotates but engine does not attempt to start. Electric and manual start.

    • Remove a spark plug, reconnect it and hold it against engine block. Keep it there while turning engine over.
      • Does it make a hot, blue spark when attempting to start? If no, troubleshoot ignition system.
      • Has hot, blue spark. Squirt some fuel mix (NOT ether) into the carburetor(s). Does it attempt to start?
        • If yes, you have inadequate fuel. Troubleshoot fuel system and review starting procedure.
        • If no, check that carburetor is not flooding from failed float needle.
    • Still won’t attempt to start.
      • Check compression.
        • If bad, troubleshoot mechanicals.
        • Good compression on all cylinders.
          • Check flywheel for sheared key, check crankcase for sealing at carburetor(s), inlet manifold and bypass covers.

    3. Low voltage at starter when engaged.

    • Measure voltage at battery terminals.
      • If below 12.6 volts with all electrics turned off, recharge or replace battery.
      • Measure battery voltage with starter engaged.
        • If below 9 volts, recharge or replace battery.
    • Remove and clean connections on battery-to-solenoid cable, battery-to-engine block cable and solenoid-to-starter cable. While they are off, inspect each for corrosion, broken insulation with corrosion and weak points. Replace corroded or weak cables.

    4. If problem persists, remove starter and clean all surfaces where engine block and starter connect.

RED SKY at night. . . JB

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