Re: 1984 johnson seized
Dirty carbs will cause their associated cylinder to run lean. Running lean causes pre-ignition, high cylinder temperatures, broken rings, and a bunch of other problems. In addition, a very dirty carburetor causes a serious lack of fuel in it's associated cylinder, which means no fuel = no oil
It is also possible that the carburetors were not the problem at all. Perhaps there was water getting into a cylinder, causing it to not fire. Water in there is super destructive.
I don't know what is wrong with your motor, but these are some things to consider.