01 8hp stall \ smoke issue

so my cousin and I were out fishing today trolling for stripers. for the first two hours we were at idle in gear trolling slowly and the motor ran fine . then we decided to go across the main river channel wich would have been a 1/4 mile run. after going about half the distance the engine stalled . it didn't spit and sputter or make any indication something was wrong , it was as is we turned the key off . he gave it a pull and it started right back up , but for about 10 seconds a whole bunch of white smoke came from the exhaust then stopped and the engine ran perfectly at idle...after that the pattern was the same... it would run perfectly at idle for hours on end but if you opened it up it would stall, start right back up ...puff a bunch of white smoke and run just fine at idle....we have no clue....any help would be appreciated...thanks in advance....Dimitri

"WHITE SMOKE" is typically one of two things....steam...or...vaporized, unburned gasoline. You sorta have to figure out which one it is before you can make a decision about what needs to be done.

If it is unburned fuel, then the carb may be loading up badly with all the trolling and idling. You may need to just pop it into neutral from time to time and "clear it's throat" by revving it up a few times and then go back to trolling.

If it is steam you are seeing, then that could be the beginning of a real headache because that would indicate water is entering the combustion chamber somehow. Usually due to a bad head gasket or a cracked head or engine block.