merc 90 hp 4 stroke carb question

[oteps]

90 hp 4 stroke on a pontoon. It has a stumble at low rpms and I was thinking of pulling the carbs off and cleaning them. But cant find a carb rebuild kit. Buying all the o rings and parts from merc is expensive. I really don't want to clean everything and reuse float and intake o rings. Any ideas? Or just deal with it? Its not my boat, just take care of it and a small cabin on the river for some friends.