The heat of the welding could have damaged the gaskets of the lower plate where water flows and is leaking out into the cowling near the front where the welding was done. Looking under the carbs at that location when running the motor on muffs or in the water, will tell the story. JMO
Oldman570
I don't think it's heat from the welding -- we completely removed the motor from the mount to have it welded...
It will be that gasket or the exhaust plate gasket, as suggested, run it and watch.....