Volvo Penta 4.3 carb revving high after a run

[jimmbo]

Are you sure it's the carb? Your engine has a Mechanical Advance distributor doesn't it? Perhaps the timing isn't retarding as much or as quickly as it should upon return to idle? Sticky weights, weak or broken springs of the advance mechanism?

 

[QBhoy]

That's a thought jiimbo, but I'm pretty sure it's carb related now.
It isn't my boat, it's my good friends (which I end up maintaining).