It is not a bad idea to open the engine up to inspect in most cases. Did it run before? Does it spin on the starter? You may even want to do a pressure check which may not be necessary for a fresh water engine.
It is not difficult to cobble a stand for an A-4 and once on the stand (or even on the floor) you could do a compression check. If the compression is suspect it's a lot easier to tear down out of the boat. And with a stand you can even run the engine before reinstalling.
Do you know anything about how it does or doesn't run?
Dave Neptune