1994 290 7.4 liter engine running rich

[ljessie]

I have a 94 sundancer 290 with a single 7.4 liter (carb). Been having trouble with rich exhaust fumes entering the passenger area while operating slowly. I understand the station wagon effect although this is too rich. There is also black soot present on the exterior of the transom and an oily gas sheen visible on the water's surface behind the boat. I took the boat to a local marina to have the problem addressed. They changed the thermostat and charged me $300.00. They said the motor wasn't heating up enough and was running with choke partially closed. I put it in the water first time since repair and no change in symptoms. Any ideas what it could be?

 

[rondds]

Pull the flame arrestor while the engine is cold. See if the choke is closed - it should be. Then start up. See if the choke opens after a few minutes. If it doesn't you've got a problem with the choke. My boat has a real old fashioned choke. As the engine heats up it heats a flat spring mounted on the intake manifold. When the spring heats, it changes the position of the spring which moves the link which opens the choke. Primitive but works.