How to Synchronize Two Engines on a Boat

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Owners of multi-engine boats strive to keep the engines synchronized or running at the same revolutions per minute, according to The website indicates that a difference of as little as 15 rpm between the two engines can cause the boat to vibrate, which can damage the propellers and bearing and make handling the boat difficult. Uneven engine operations can also adversely affect fuel efficiency. Adjusting the individual throttles to matching speeds can be difficult and tedious, as it will need to be done every time the speed of the boat is adjusted. An automated engine synchronizer eases the process of keeping a multi-engine boat running smoothly.

Items you will need

  • Boat (twin engine)

  • Synchronizer

Install the synchronizer according to the manufacturer's instructions. This will include running cables from a synchronizer to the point where the tachometer cable attaches to the engines. The installation will also include cables to the throttles. Estimated installation time, for a professional marine mechanic, is about 10 hours.

Turn on the synchronizer and adjust the throttle of the lead engine. This engine is determined at the time of installation. The synchronizer will adjust the throttle of the other engine to the same speed as the lead engine.

Disengage the synchronizer any time the engines need to be operated individually. Incidents such as docking or turning the boat sharply require individual operation of the engines.


  • The synchronizer will shut down if it is unable to match the rpms of the lead engine.


  • Manual synchronization, through adjustments of the throttles, is best accomplished with the aid of high-end digital tachometers. Other boat operators rely on the sound of the engines and the feel of the boat in synchronizing the engines.
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