Pull a battery from a vehicle, or jumper the outboard to start it. You want to first check the oil--be sure that there is no water in the oil.
Be sure and put on the "Muffs" and have water running to the lower unit, so you won't damage the impeller or engine by running it out of the water.
There is a good chance that the engines will be fine, but should have some work done on them...they will have carburetors, and those may have to be cleaned, if the engine was not run out of fuel, or the carburetors were not drained. (which should always be done if you are not going to use the boat for more than a few weeks. So, the engines may or may not even start--depending on how bad the carburetors are.
The fuel will be no good, and the tanks will have to be pumped out, and the old gas disposed of. You will probably want to replace all of the fuel lines. Probably new spark plugs, new lower unit oil, change the engine oil before running the motors on a body of water.
I would not be afraid to buy the boat if you could not start the engines, but price it to replace the engines.
% the engines are totally shot? 10%-- You cannot really say if they are or not without running. The 1200 hours--depends on how well they were maintained, if run in salt or fresh water and how the engines were run.