43L OMC 2 Barrel Carb Vacuum Choke Problems

"Noticed the carburator was ru

"Noticed the carburator was running rich after warm up. I pulled the air breather (which had black soot on the metal screen) off the 2 barrel carb and noticed the choke flap was only half open. This vacuum choke system has one tube that runs to the intake manifold which has constant vacuum. The strange thing is there is a second hole beside the tube on the intake manifold that was open and also had constant vacuum. This did not seem right to have a vacuum leak so I machined a plug and inserted it into the second hole. I ran the engine and allowed it to come up to temperature and then adjusted the choke so that the choke flap was almost completely open. This choke system now does not operate correctly during a cold start up causing a hard to start problem. If the choke is adjusted to operate correctly at start up it will not open over the half way point afterwards. The tube between the manifold and the choke never gets warm and the housing for the choke adjustment also never gets warm so obviously the bi-metalic strip in the choke housing has no reason to expand to pull the flap open. Any advise, thanks"

"It sounds like your heat pick

"It sounds like your heat pickup from the manifold is open to vacuum. Since I mostly worked on cars, I can't be sure without looking, however there is a source for heat in the manifold. The vacuum, in the carb, draws heated air from the manifold up the tube to the choke. There used to be a electric conversion for different auto carbs. If they knew make and model of carb someone else here or a marine parts dealer might have the information. The hole you plugged was the air intake. Heat chamber prob. rusted or cracked open to vacuum."

"Or, sorry about my slow brain

"Or, sorry about my slow brain at 70,the vacuum you plugged was the draw from the carb and now the choke is getting no flow of heat. It could have been a coked up choke and needed cleaning out of carbon/dirt and adjustment."

"thanks for responding; you ar

"thanks for responding; you are correct I plugged the draw tube for the choke. Typically you should prevent vacuum leaks however this design does involve a vacuum leak. The carb is the vacuum source which draws air from this hole I plugged, this air is heated as it passes through the metal tube in the intake manifold chamber. This hot air also pass through the choke housing heating the bi-metallic strip. I undid my screw up yesterday and the choke is operating correctly now. I would like to eventually replace the intake manifold and carb for a 4 barrel setup with a electric choke. Thanks for your help.}"