The magneto in an outboard ignition system uses permanent magnets and pickup coils to produce AC voltage. That AC voltage gets triggered from the ignition points, which fire the spark plugs at the precise instant at which maximum compression occurs. The coil ends on the magneto can become burned and corroded, causing weak spark and a rough running engine.
Things You'll Need
- Boat engine repair manual
- Socket set
- Ratchet wrench
- Flywheel strap
- Steering wheel puller
- Carburetor cleaner
- New magneto
- Torque wrench
Set the engine tilt so the motor sits vertical, by activating the electric trim motor or adjusting the manual pins on the engine tilt bracket. Activate the main ignition cutoff switch, or disconnect the negative battery cable with a socket, if so equipped. Unclasp the top cowl case on the engine by uncoupling the snaps or removing the bolt fasteners with a socket. Pull the case off and set it aside, taking care to keep the rubber gasket intact in its groove.
Place a flywheel strap around the outside edges of the fly wheel and pull taut. Use a socket to loosen and remove the flywheel nut. Place a steering wheel puller over the flywheel and align the three puller hooks to the inside of the flywheel holes. Turn the threaded puller bolt in by hand until it contacts the depression in the flywheel shaft. Use a socket and wrench to turn the puller bolt clockwise to break the flywheel loose. Pull the flywheel off the shaft.
Disconnect the plug wires from the spark plug or plugs. Remove the boots from the plug wire ends. Use a socket and wrench to remove the mounting bolts on the stator -- the large circular ring that houses the magneto coils. Gently pull the stator upward, guiding the plug wires through their guides. Clean the underside of the stator and stator ring with carburetor cleaner and a rag.
Remove the magneto coil bolts with either a small socket or large flat-head screwdriver. There should be two or three bolts per magneto coil. Loosen the screws to any ground wire attached to the stator housing. Pull the magneto coils out, along with their wires.
Thread the plug wires from the new magneto coils back into their guide holes and set the new magneto coils into their mounting guides. Screw the magneto coils down with their bolts into the stator housing, using a screwdriver or socket. Place the stator housing back into position and insert the mounting bolts. Screw the stator mounting bolts down with a small socket.
Place the boots back over the ends of the plug wire or wires and reconnect the plug wires to the spark plug or plugs. Set the flywheel down over the flywheel shaft and press it firmly downward as far as you can. Place the flywheel strap around the edges of the flywheel and hold it taut. Tighten the flywheel bolt down with a socket and wrench. Refer to your owner's manual for the proper torque in foot-pounds for the flywheel bolt. Torque the nut to specifications, using a torque wrench.
Place the engine cowl case back on the top of the engine. Align the case gasket properly. Fasten the clips by hand, or screw in the bolts with a socket if it has bolt fasteners. Deactivate the cutoff switch and reconnect the negative battery cable with a socket, if so equipped. Start the engine for test, with the lower motor unit in water.
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