Tohatsu Electrical and Charging: charging output basics
Some Tohatsu outboards barely charge at all, while larger models can comfortably maintain a starting battery and basic electronics. Here is how outboard charging works, what to expect by engine size, and how to check charging output properly.
Tohatsu outboards generate electricity using a stator (charging coil) under the flywheel. That power is then managed by a regulator/rectifier to charge a 12V battery and run accessories. The key point is that outboards do not charge like a car alternator at all times, and charging capacity varies hugely by model.
Charging methods across outboard sizes (what to expect):
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Small portables: often have no battery charging, or only a small optional charge coil intended for light loads.
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Mid-range engines: commonly offer a charging coil + rectifier/regulator, usually enough to maintain a battery and basic electronics if loads are sensible.
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Larger outboards: typically provide a higher-output charging system that supports more onboard electronics, but it still depends on idle time vs cruising RPM and your total load.
How to check charging output (basic test):
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With the engine off, measure battery voltage (a healthy battery is usually around 12.6V when rested).
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Start the engine and measure again at idle, then at a fast idle. You should normally see voltage rise into the 13V–14V region on a working system (exact numbers vary by regulator and battery type).
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If voltage never rises, check the main fuse, battery terminals, earths, and the regulator/rectifier connections for corrosion.
Common causes of “not charging”: loose or corroded connections, blown fuse, failed regulator/rectifier, damaged stator coil wiring, or the engine simply not being fitted with the charging kit.
