Check your battery to ensure there is minimum of 12.4V, 12.7 is even better.
Take a look at the inside of your distributor cap and rotor. Contact points should be clean.
Pull a couple of plugs and see if electrodes are clean and dry. Be sure to vacuum the spark plug tunnel before removing the plug so rust doesn't get into your cylinders.
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine