The dry weight of a 2002 model, 75hp Mercury outboard 4 stroke, is 386 lbs.
the ignition timing set wronge. BAd accelerator pump in the carburetor
where can i find an owners manual for a 2003 75HP mercury outboard
thats not a valid serial number
No, backfire is usually caused by park plug wires that are installed incorrectly or an engine that is out of time. Fuel filter and pump will not cause backfire.
Incorrect Timing Can Cause Backfire.
Having no catalytic converter installed is illegal and can cause a myriad of problems. Probably not a backfire though.
Yes
It's your switchbox, I just did this on my 75hp 4cylinder.
The engine may not be very good or too small and you may be giving it too much gas, thus flooding the engine. I'm not sure but this could be the problem.
Normally you do not get carbon buildup on injectors. They can get gummed a little, or blocked, but that should not cause backfire. Check timing.
The chain can not backfire. If it is installed off time it can cause a backfire, which could conceivably damage a starter.