87' 48 spl help

[lazylightning]

just put motor on boat that has sat for a while.starts right up and runs good. good bottom and top end. run at idle 5 to 10 min. then pick it up and will run great for 2 to 3 min. then boggs down and won't pick back up. let sit over night does the same thing. ball stays hard the whole time not rock hard. any help would be great

[boats.net]

You should remove and thoroughly clean the carburetors. The idle circuit sounds to be clogged.