We have a 2005 Suzuki 15hp 4 stroke outboard, runs fine for say 20 minutes and then on slow running will cough and play up and we try and nurse it with a bit of choke but not successful. Then it?ll be fine for another half hour or so! I have stripped the carb and sprayed carb cleaner every where, drained all fuel and replenished along with a service. Can anyone help please?