Was given a 1960 mercury outboard and was told it ran last time used but it had no spark plugs in the cylinders and was outside for 4 years would that have harmed the engine?

Turn it without spark to make sure it isn't seized before you do anything. Shouldn't harm the engine, but you might want to pull the rods and make sure there is no rust on them. If you clean them very well (ex. soak in fuel or carb cleaner, then scrub with wire brush) they should last quite a while. I would suggest getting new oil rings and making sure the crankshaft doesnt have rust either.