Agreed more info would be good. Your carb is old enough to have had the power valve ruptured from a backfire. Holley part #125-500 is an update for 1989 and older carbs. To test your power valve, while holding the large end, try to turn the small end. If it will turn, the valve is shot. If it won't turn, the valve still works. A blown power valve goes to full rich and the boat is barely drive-able, and will be leaving some black smoke.
Another possibility for running rich is a choke set too rich. Your choke should open fully within one minute of start-up.
CUSTOM WHEEL & TIRE PACKAGES
$125 LED LIGHT PACKAGE - FREE SHIPPING
REBUILDING HOLLEY MARINE CARBURETORS - $249 DELIVERED
Email - email@example.com