Tohatsu Ignition and Spark: spark test basics and common no-start checks
If your Tohatsu will not start, misfires, or runs rough, a quick spark test can save hours. Here is the safe way to check spark, what a healthy spark looks like, and the most common ignition faults.
A strong ignition spark is essential on any Tohatsu outboard. If the engine cranks but will not start, or it starts then misfires, do a spark test before replacing fuel parts.
Spark test basics (safe method)
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Ventilation and safety: Keep the area clear of fuel vapour. Remove the safety lanyard until you are ready to crank.
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Use an inline spark tester: Fit it between the plug lead and the spark plug. Crank the engine and look for a bright, regular flash.
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No tester available: Remove the spark plug, reconnect the lead, and ground the plug body firmly to clean engine metal (never hold it by hand). Crank and look for a snappy blue spark across the gap.
What to check first if there is weak or no spark
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Lanyard and stop switch: A faulty kill circuit can shut spark off completely.
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Spark plugs: Fouled, wet, cracked insulator, wrong gap, or wrong plug type. Replace if in doubt.
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Plug leads and caps: Corrosion, loose fit, damaged insulation.
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Connections and earths: Clean, tight, and dry.
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Battery voltage (EFI models): Low voltage can cause weak spark and odd running.
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Fuses and ignition wiring: Especially after storage or water ingress.
If you have spark on one cylinder but not another, suspect the plug, cap, lead, or coil on that cylinder. If there is no spark at all, the kill circuit, wiring, or ignition module side may need deeper diagnosis.
