I've had a 15 yami come completely off the transom and run like a cartoon for about 20ft. until it came to rest on a sandbar about 2ft deep running all the way.
It still runs to this day..
But, I immediately power washed, corrosion x'd the whole thing, took the plugs out, flushed everything with gasoline and finally dumped 2-stroke oil everywhere and turned it over to flush it several times by hand before running it..
When I did start it up, I ran it at 15:1 mixture until I was sure it was safe, changing the fouled plugs every hour or so..
I've dunked 3 engines...... all 3 running.......... :
All three still run to this day, although I've sold two.
First thing you want to do is get all the salt water out of where it shouldn't be, hose it down ASAP if possible. Next is get the water out of the cylinders and the fuel system. I spayed WD40 (water displacer) in the cylinders and then pulled the motor over with the plug holes facing straight down until no more milky water junk comes out. I drained my fuel lines and my carb bowl and sprayed carb cleaner into the throat of the carb and the lines.
Next you need to make sure your ignition system is dry. The only motor I've ever had to put parts into after dunking was the only one were I didn't make sure the ignition was dry. (I fried the power pack after getting it running for about 30 sec. with a wet ignition.) On my motors I soaked all the ignition parts, connections and under the flywheel with WD40, Then I waited as long as I could bear for the WD40 to evaporate, wiped down all my wires and gave her a go. One of my older motors had points and I had to wait till the next day when the points fully dried out to get spark, but most of the CDIs will tolerate a good dunking.
Just keep in mind, saltwater is the enemy. Any salt residue you don't get rid of will start on your ignition pretty fast.
BTW, bolting your motor on, or at least chaining it on, is a good idea too.... trust me!