I had my 1990 25HP Johnson (TJ25ELESE) at WOT today and it suddenly stalled-out and died. It had an excellent "pee" stream and the overheat alarm never sounded.... so I don't think that it overheated.
The only way that I could restart it was my priming the carb by the usual pushing in (pumping) the key while turning on the ignition. It would start and then almost immediately die. I could keep it running by continually pumping the key. As soon as I put it in gear, it died. I could never get it to rev up by advancing the trottle.....it would just die.
The gas was brand new from the pump and I doubt that it contained any water.
What do I need to do to diagnose and correct this problem?
run a clear fuel line from the fuel pump outlet to the carb bowl inlet....as you pump the primer bulb from the fuel tank you should see fuel flow to the carb bowl through the line. When the primer bulb gets firm the carb bowl is full and the engine should start and run at least momentarily with the fuel already in the bowl. As the motor runs look for air bubbles in the clear line. If they appear, air is getting into the system somewhere. If the primer bulb collapses, you've got a restriction somewhere between the fuel pick up in the tank and and the bulb. By continually squeezing the primer bulb, you should be able to operate the motor as this action replaces the fuel pump itself.
If no bubbles appear in the clear line, then possibly you've gotten some bad fuel or it's time to check the ignition system.
I took the carb bowl drain nut out and sprayed an aerosol carb cleaner through what I thought to be the High Spped Jet. I then added 8 oz Sea Foam to about 1 gal of mixed fuel and ran the motor for about a half hour at a medium speed. It coughed and ran rough then seemed to smooth out. I switched to the regular tank and tried it out after adjusting the idle jet.