Recently bought boat(19') with motor above, took for test ride and didn't miss a beat. Went out next day and motored for about 30 mins, engine went from around 4000rpm and died to around 1000 rpm. Managed to limp home at around 10mph. Almost like running on only 2 cylinders. Replaced fuel water seperater and engine filter stripped 3 carbs and blew out jets etc new plugs still the same. Tried aux fuel tank don't think fuel is a problem as carbs etc were clean. Any suggestions
