you can tell if the engine is running to lean because it will eather do one of 3 things....first just die, second squeal like a lil pigy and there will be NO smoke comming out of the exaust, third the engine will dead stop an you will hear eather a crack, boom, or pop......non of these are good.....i've busted a few engines and let me tell ya you dont want to do it...you dont want to lean the engine out right away you need to put about 3 to 4 gas tanks of fuel through it to make sure its broken in an lubricated....these moters are dead stiff once they get out of the facotry. read the engine manual...i believe its the dynamite .15.....i had that engine in my first boat...an it sucked but once i broke it in it was alright.....when it vapor locks take the plug out an punch the fuel line an pull the pullstart to get all the fuel out of the piston. then lean out the highspeed about a quarter of a tern.....its a very very tuchy needle valve.....wait till you get into the real stuff an have a third chanel on your boat so u can tune out the engine while its in the water an going....its a life saver an it gets going much faster...Good luck.