20p6 Merc 6hp 4 stroke--runs on half choke, revs up and stalls

[Wakelinj]

Hi all,

Just as the title says. Choke to start, then down to half choke or it won't run. After a few seconds it will rev up and quit.

This is a fuel starvation situation, usually the carb, I know. Carb has been cleaned and it's spotless. Can't find a fuel leak anywhere.

Could a weak or perforated fuel pump diaphragm cause this? Any other culprits?

Before you ask, spark is strong, compression is 120psi.

Thanks for your wisdom

 

[airshot]

Just cleaning the carb may not remove gunk from those teeny tiny passages, use a wire or blow air thru to be sure they are open. If it did run well in the recent past, but doesn't now....you have a blockage somewhere.