You got sound advice above. replace it. where oil leaks out, water will seep in, and jb weld is temp repair only. Find a nice used lower unit. if a late 80's early 90's 140hp evinrude will interchange, 20' LU, PM me, a friend has a complete one cheap. seems to be good shape,the housing is very nice. shaft splines are good.Internals need to be gone over.

Thanks guys. I'm glad that I've got an old enough motor to find used parts easy on craigslist. Looking at one thursday for about $150. If it doesn't work out I do believe a 140hp would work. I'll send you a pm if so.

check the paly in the input and output shaft, a little in/out slack is normal. The carrier spanner washer/nut that holds the carrier bearing into the open end of the LU is also a suspect area to check. lots of time the spanner nut will have the threads trashed, not allowing the spanner to hold the carrier bearing in tight causing leaks and too much slop on the gear mesh.This spanner nut is the threaded ring inside the LU where the prop shaft comes out of the housing.It holds in the bearing.
watch for a lot of corrosion around the input shaft at the water pump housing. I'd pop the water pump off to inspect as you'd want to replace the old impeller anyways. Too much corrosion will cause poor water pressure and possible breakage if corroded /pitted deeply.