Re: 1984 50 hp Mercury Water in #1 Cylinder
If it's coming from the area where the cyl block water jacket cover seals around the spark plug holes, it's just a leaky gasket that can be replaced.
You do need to be careful when removing the 1/4-28 bolts as they have a tendency to seize in the block and snap off if too much force is used. Instead, use a heat followed by penetrating oil (as required). A propane or MAPP portable torch should have plenty of power for this job.
The gasket you need is Merc P/N 85487.
If you're in a pinch and have to get it out on the water, just clean around the leaking area and temporarily seal it with red hi-temp RTV sealer.
HTH...........ed