Twin 350 GM 1966 boat totally raw water cooled not closed system. Engines have been running great. Today heading out idled the engines for about 20min waiting for my passengers. Port engine stalls. Restart stalls acts like carburetor issues. Out of gear she revs fine. Put in gear will idle rough then stall. Got her idling messed with the carb. Accidentally put my hand on the left exhaust manifold burned my hand. Right side exhaust manifold still nice and cool. Blocked water intake to that exhaust manifold???