There are several components to inspect and test when a Johnson outboard motor won’t begin to work. But before you begin to troubleshoot a boat motor that won’t start, make sure the battery is fully charged, all cables and wires are tightly connected, and the shift lever is in neutral position. Follow this guide to find the cause and solution for a Johnson outboard engine that will not start up.
Electric starter system
So your Johnson outboard will not fire up, but does the engine turn over with continued cranking? If the answer is yes, does the flywheel rotate? If the flywheel does not rotate (or turns slowly) check the battery’s charging condition or the terminals for corrosion or a loose connection.
If the engine turns over with continued cranking, does the starter rotate? If the starter rotates, check the starter magnet switch. Also check the pinion and overrunning clutch. Refer to the factory service manual for inspection and testing procedures.
If the starter does not rotate, check the battery’s state of charge, check terminals for corrosion and tight connections, and check the 20A fuse and fuse case. If everything checks out fine, check for a “click” sound coming from the starter relay when turning the ignition switch to start position. On tiller models, check for the “click” sound when the starter button is depressed.
If there is no “click” sound coming from the relay, the problem could be the neutral switch, ignition switch, starter button, starter relay, starter relay and ignition switch, or there could be wiring problem between the starter relay and ignition switch (or starter button). Refer to the repair manual for inspection and testing procedures.
If there is a “click” sound when turning the ignition switch to the start position, remove the starter from engine and bench test it. Does starter motor turn under no-load conditions by connecting battery (+) terminal to “M” terminal of starter motor and battery (-) terminal to the starter motor body? If the answer is no, check the armature coil or the brush and brush holder. Refer to service manual for checking procedures. If the answer is yes, the magnetic switch and or connection is faulty and it must be replaced.
The Johnson outboard’s ignition system is the system that produces the spark to ignite the mixture of air and fuel and includes the spark plugs, battery, ignition coil and other switches and wiring. If the engine is hard to start, perform the following ignition system tests to determine the cause and solution to the problem.
Check spark condition using a tester gap, set tester gap at 5/16. If spark is good, check ignition timing by using a timing light. If there is no issue with timing, replace the CDI unit.
If there is a weak or no spark, check the spark plug(s) condition. If the spark plug is bad, replace it. If the spark plug is in good condition, disconnect the engine stop switch wire (see manual for wire color). If it sparks, check and or replace the engine stop switch. If no or weak sparks, check ignition coil resistance (see service manual for ignition coil resistance specifications).
If ignition coil resistance is out of spec, replace ignition coil. If the ignition coil resistance is good, check the spark plug cap for any evidence of high-tension leak. If there is a leak, replace the spark plug cap. If there is no evidence of a high-tension leak, check the spark plug cap resistance and replace if if it’s out of spec. If the spark plug cap is within factory spec, check consensus charger coil resistance. If it’s out of spec replace the coil.
If the condenser charge coil resistance is within specifications, check the pulse coil resistance. Replace the coil if the pulse coil resistance is out of spec. If it’s in spec, check the CDI unit, if the CDI unit is out of spec, replace the CDI unit.
Always use a factory service manual when checking or preforming tests to the Johnson’s ignition system.
Fuel System (carburetor models)
It’s important to check or test the fuel system when a Johnson outboard will not start. Here are a list items to check:
- improper starting procedures. Refer to starting procedures in service manual.
- Clogged fuel filter.
- Poor quality or old fuel.
- Fuel tank vent or hose restricted.
- Faulty anti-siphon valve.
- Primer solenoid inoperative.
- Plugged solenoid filter.
- Primer hose improperly routed.
- Restricted or mis-routed fuel supply lines.
- Restricted fuel pick-up.
- Plugged primer fittings or hoses.
Johnson outboard won’t start (misc. items to check)
The list of items below are random areas that should be checked when a Johnson outboard motor will not start. Always keep in mind that more than one problem can be present.
- Stop circuit grounded. Inspect the wiring for emergency stop switch. And make sure the safety lanyard is installed properly and the stop circuit is not grounded.
- No fuel. Ensure there is gasoline in the fuel tank.
- Water in fuel. Sample the fuel from the fuel return manifold and check fuel filter.
- Air in fuel system. Check for air in fuel supply manifold.
- Low or now fuel pressure to fuel injectors. Test fuel manifold pressure, refer to factory service manual for checking procedures.
- Excessive fuel or oil, engine flooded. Check for fuel leakage at injectors, leaking fuel or oil lift pump, or leakage coming from vapor separator vent.
- Fuel injectors not working. Test for voltage at fuel injectors.
- Low or no alternator output. Check voltage and circuit. Refer to repair manual for checking procedures.
- No compression. Perform cylinder compression test.
- Internal powerhead damage. Inspect engine and repair as needed.
- Fuel supply restricted. Check anti-siphon valve, primer bulb, fuel pick-up and inspect fuel system for leaks.
- Crank positon sponsor (CPS). Test crank postion sensor.
It’s highly recommended to use a factory service manual when troubleshooting a no start issue. More advanced information can be found in the book.