Re: 7.5 mercury will not start
Are the plugs wet after trying to start it. If so then your problem may be in the ignition side. If the plugs are dry then the likely problem is fuel delivery which could be a number of things such as stuck float valve, incorrect float height,incorrect mixture setting, or a simple as a bit of crud stuck in the line between the tank and the carb. You could try putting a little fuel into the carb throat whilst someone else pulls the engine over. If the motor starts or fires then you will be more guided toward the fuel system. It would be then a matter of going through a systematic check of the fuel side to ascertain where in your system the fault lies.
<br /><br />Check out the Engine FAQ section. "Outboard wont start" should put you on the right track.<br /><br />Good luck.