Car and Boat Distributors: [Differences and Examples]

A distributor is a device that will cause the ignition coil in an internal combustion engine to produce sparks at the appropriate time in the power cycle. They take their input from camshaft rotation and provide either high voltage at low rpm for ignition or low voltage at high rpm for the spark plug.

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Top 5 differences between car and boat distributors.

  1. Car distributors usually have an adjustable arm on them so that you can advance or retard the timing. Sometimes they will also have a vacuum advance which provides the timing at low engine speeds and brings it back as rpm increases. This compensates for the lack of air coming into the intake manifold that allows for earlier ignition timing below idle.
  2. A marine distributor would not have this advanced function and most often not even a vacuum advance. They will also be lighter than an automotive distributor because of the lack of metal in the rotating mass.
  3. Car distributors are common on older American V8’s and almost always found on domestic cars. Most imports after 1980 use coil packs instead of distributors.
  4. Marine distributors would be found on any engine with adjustable ignition timing. For example, they are used often on outboard engines to allow for increased horsepower at high RPM by advancing the spark timing. They
  5. Car distributors would be very hard to find on a boat because they are not designed with the saltwater environment in mind. For this reason, most boats use coil packs along with electronic ignition modules that act as both distributors and coil.

Can I use a car distributor on a marine 350?

No, you can not use a car distributor on a marine 350, because a car distributor is not an ignition-protected part, and using it on a boat may cause serious injury to yourself and others.

To be clear, NEVER use a car distributor on a marine 350. Any crank-fired ignition that is not built into a marine product or wired into a marine harness will cause the risk of fire.

Boat Distributor functionality

The boat distributor is a device connected to the ignition switch, which stores up enough power from the battery to fire spark plugs that distribute sparks to each cylinder at precisely timed intervals. For most modern boats, these distributors consist of four cylinders like those found in cars but some older boats such as small outboard motors may only have one or two. Each cylinder has a rotor inside which houses an insulated stud and ball bearing. This bearing is what makes contact with the spark plug cable and distributes sparks to each of the four cylinders, hence the named distributor.

Because this device controls both ignition timing and power flow to the engine, distributors are critical for an effective engine.

The functionality of boat distributor:

  • Primary functions of the distributor on a boat include
  • Distributing power from the battery to each spark plug
  • Distributing sparks to each cylinder at exactly timed intervals during operation of the marine motor
  • Ensuring that ignition timing is correct and consistent
  • Preventing minute drops in voltage throughout the electrical system by ensuring that all power flows through the spark plug and out to each of the four cylinders.


Car distributors are the single part that transfers the signal to fire the spark plugs, while boat distributors are two separate parts, one for each ignition coil, and often contain an electromagnetic switch or power transistor to control high voltage coming from the ignition coil. Most importantly they can never be substituted as a replacement for the ignition module on a marine 350 and can cause serious injury if used.