1973 mercury 850, thunderbolt ignition
motor has ran fine, ever since i rebuilt the carbs. ran it several hours since the carb rebuild, no problems whatsoever.
a couple days ago i ran a tank of gas that had sat over the winter and until now. i did add stabil to it before storage.
as soon as the motor picked up this gas, it wouldnt run at high speed.
runs great at idle and 1/4 throttle. i can push the throttle all the way up but the motor will only run at 2500 rpms, and about 5-10 mph (normal full speed is 35)
got fresh gas in a different tank, same problem, but i did run the engine long enough ( at least 1/2 to 1 gallon of fuel) to get the old fuel out and new fuel in.
so i went home and changed the plugs. they did look awfully dirty. they are the style that is just flat on top, no gap to set (hope this makes sense)
went back out with the same new gas. motor ran great for 5 minutes, then bogged back down, doing the same exact thing.
havent checked the pluggs again yet, as it is dark.