50 merc just won't restart

[mercerfisherman]

Hi. 1984 Mercury 50 hp, 4-cylinder, 2-stroke. Fires up great when cold. Runs great. But after driving it and then turning it off, it just won't restart. Engine cranks fine, but it just won't start up again. Only after I wait for about 15 minutes to a half hour will it restart. Sometimes, I find myself flooding the engine with gas trying to get it to restart so I have to wait to try and start it again later. This has been an ongoing problem for years... any ideas? Service in the past: new switchbox, new stator, new plugs, (plugs show clean and dry) new fuel pump, new gas tank and hose. Any help would be appreciated.