We have a 78- 80 hp mercury outboard motor on our boat. It has a dual carburetor. We've adjusted the fuel mixture. We use 50:1 gas mixture. We'd like to know how do you adjust the carburetors? Also, how do you adjust the spark on it? What is the spark control on it,and what does it do? We've put all new gas lines on it,(some were worn, as someone had suggested.) We still have the hesitation when giving it gas and it idles very rough.email us at: eddjn@adelphia.net