I recently purchased a 1987 motomarina sebring, but am having some trouble with the choke. It seems to run fine in full choke mode, better in half choke, not at all with no choke. Its as if it gets too much air if the choke lever is fully open. I have checked the engine for air leaks (though not thoroughly) I simply held a finger over the air intake to see if it would sputter out quickly, and it did. I don't really know how to go about addressing the problem from here, as I am very new to repairs. Any advice would be greatly appreciated.