Okay as the subject sugests my 86 Merc 170 overheated this weekend and now it won't start. It turns over fine but when I pull the coil wire and try to get it to jump a spark I get nothing. It has an electronic ignition conversion so maybe the problem lies there? Swapped coils, still nothing. Cap, rotor, and electronic ig. look fine. Put old points and condenser back in still nothing. Read the volts from positive on bat. to coil pos. shows 12.5, however when the key is on it drops to about 6.5! (burned wire maybe?I can't see one!) I will try to jump from pos. on bat. to pos. on coil tonight unless anyone has a better idea?? Also checked cylinders no water, plugs and wires look fine. Major water leak at the water pump, (the cause of the overheating problem) but it is dripping down into the bilge not onto anything important. I think I tried just about everything I can and I read lots of posts so maybe some of you more seasoned veterans have seen this before. Thanks in advance.