The automatic electric choke works on a switched 12v circuit and has a spring mechanism housed in a plastic cover located on the side of the carburetor. These chokes are electrically heated to promote expansion and contraction. When the engine is cold the spring contracts, coiling more tightly. This contraction pulls on the choke rod and puts pressure on the choke to close completely. When the engine is started, the closed choke creates more vacuum in the engine, pulling in more fuel. As soon as the engine starts, a vacuum is applied to the vacuum choke pull-down servo, which in turn pulls the choke open slightly--just enough to allow enough air into the engine to keep it running. As the engine continues to warm up, the electrical choke responds to the heater inside and begins to expand and as it does, it begins to push the choke open.
1989 MasterCraft TriStar 190 SE