12V Starter for MerCruiser, Mercruiser Stern Drive, OMC, Autocar, Thermo Electron 1976-1999

This one is 12V. Voltage has to match your machine exactly. A 12V unit on a 24V system will be damaged, and a 24V unit on a 12V system will crank slowly or not at all. If you are unsure, check the battery setup: two 12V batteries wired in series usually means a 24V system.

This unit turns counterclockwise. Rotation is read looking at the drive end, the end the pulley or gear sits on. A starter that spins the wrong way cannot engage the flywheel, so this is not a detail you can work around.

We list 45 vehicle and equipment applications for this starter. Use the "Does it fit?" checker further up this page to pick your make, model and year, or open the full applications list.

The surest check is the number stamped on the unit you are replacing. Match it against the cross reference numbers on this page. Fitment lists are a guide, and the same machine can leave the factory with more than one setup, so the number on your old part beats a model year every time.

Probably yes. One unit is sold under many numbers by the vehicle maker, the original manufacturer and the aftermarket. The cross reference list on this page shows the numbers we know map to this starter. If yours appears there, this is the right part.

If your number is not listed, try our cross reference lookup. It searches every number we hold, not just the ones shown here.

6423 is the Lester number. Lester is the long standing industry catalogue for rotating electrical, and its numbers are how the trade identifies a unit regardless of who sold it. We use it as our part number because it is the one identifier that stays stable across every brand that has ever boxed this starter.

One loud click and no crank usually points at the solenoid or the battery connection. Rapid clicking is nearly always a flat battery or a bad ground, not the starter. A whirring noise with no engine turning means the drive gear is not engaging. Silence with good battery voltage points at the ignition switch, a relay or the starter itself.

Before replacing anything, load test the battery and clean both cable ends. A poor ground imitates a failed starter closely enough to sell a lot of unnecessary parts.

The tooth count is the number of teeth on the drive gear that meets the engine flywheel. It has to match the flywheel it engages. A starter that is otherwise identical but carries a different tooth count will not mesh correctly and will chew the ring gear.

Count the teeth on your old drive gear if you are unsure. Our glossary explains the rest of the spec vocabulary.

A gear reduction starter puts a small gearbox between the motor and the drive. It spins a smaller, lighter motor faster and gears it down for torque, so you get more cranking power for less weight and less current draw. Direct drive starters skip the gearbox and are simpler but heavier for the same output.

The two are not interchangeable by eye. Match the mounting and the part number, not the look.

New. Every starter we list is a new unit, not a rebuilt core, and it carries a one year warranty. There is no core to return and no deposit to chase.

Orders leave within three business days. Ships from USA. You can read the full terms in our shipping policy, and returns are covered in the return and refund policy.

Returns are accepted within the window set out in our return and refund policy,and a restocking fee applies unless the part is defective or we made the error. A unit that has been installed or used cannot be returned, so it is worth confirming fitment by part number before you fit it.