Tilt the motor up, now while up grab hold of the prop end and see if you can move the motor up and down? Should be no movement! or you may need a transom.
Get up in the boat and walk around heavy and see if there is any soft spots in the floor? The hatch above the gas tank might be soft, but is a pretty easy fix.
Do you have a compression tester?? They are not to much to buy one if not, warm motor up a bit, then take plugs out and test all 6 holes. More important then how high they are the rule is they should all be with in 10% of each other.
Crack the screw in the lower unit, is the oil clear? If milky it has water in it. No good! Look for any metal shavings in the oil or some have a magnet that will collect it on the screw.
Check all options to make sure they work.
As stated above
good luck