1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 132Get this manual
ENGINE TURNS OVER, BUT STALLSENGINE RUNS IRREGULARLY, STOPS OR IDLES ROUGHLY 1 FUEL
Fuel tank Fuel is deteriorated or dirty Fuel hoses Leakage, Bent, Kinked, Flattened, Broken Fuel filter .Clogged Fuel pump .Worn or broken, gasket is cracked and leaky Carburetor Needle valve is worn Pilot passages are clogged Choke is closed Water is in mixture