I have a 1988 45 hp Mercury.  When I first put it in the water it starts right up and will run all over the lake, but after I shut it down it won't start again.  I have not figured out how long it takes it to recover.  I tried running Sea Foam through it with the same results.  Any ideas?

When it won't start, first thing you need to do is isolate if it's fuel or ignition related. First thing would be to pull each plug wire off, stick a #2 phillips in the wire and hold it approx 3/8" - 7/16" from a metal surface on the motor and make sure each wire is throwing a good, blue spark while cranking. If there's no or weak spark, you need to start troubleshooting your ignition system. If it has good spark, then the problem is most likely a fuel delivery problem. It could be flooding out or not getting enough fuel. Have to chase that rabit when you find out if you have an ignition or fuel delivery problem.