'97 Yamaha F50aetl

Hi,
I have an 1997 F50 AET yamaha. It is running very rich on all 4 pots. i have had the carbs apart to check and clean. There doesnt appear to be any loss in perfomance however. When i flush the engine, the motor spits out heaps of carbon from the exhaust and when it is idling in the water, there is a "puddle" of black exhaust water that gathers around the leg.
What could be causing the motor to run so rich if the carbs are clean and jetted as per standard?
Also, i have noticed my voltage guage getting as high as 15.5 volts when i hit WOT. Is this just a case of changing the voltage regulator?

cheers
mike

[boats.net]

Run a compression and leak down test to check conditions of rings. Prop it to turn between 5500-6000 rpm's.

ok, thanks. Can you tell me what the compression figure should be?

cheers
mike