Abstract: A throttle synchronizer for quickly and accurately setting and resetting each of the separate throttle valve control levers of plural internal combustion engines at a selected engine operating speed, with accurate and automatic synchronization of the engines at the selected lever setting. Adjustable throttle lever stops limit advance movement of the levers to the selected lever setting. The throttle lever stops are mounted on a transverse yoke, which is adjustable slidably relative to the paths of movement of the levers, so as to selectively locate the stops at any lever setting desired. The yoke is mounted slidably on a support located adjacent the levers, and a locking screw is utilized to secure the yoke in a selected position on the support. The throttle synchronizer is particularly useful on twin engine power boats having twin propellers, each driven by its own internal combustion engine.