Hard starting on gasoline marine engines is unfortunately not very uncommon, especially if idle for any real length of time.  We suggest a two-prong approach to combat the issue.

First, to get the engine started, we recommend spraying Berryman B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner (part #0117/0117C) into the carb or throttle body as you turn the engine over.  Usually, a quick shot or two will do the trick.
 

For a long-term fix, though, we advise using a combination fuel stabilizer and detergent-based fuel additive, such as Berryman B-12 Chemtool Total Fuel System Clean-Up (part #2616) or B-60 High-Mileage Fuel System Rejuvenator (part #7516).  Both products at 1 fl oz/gal will protect all grades of gasoline for 6 months as well as thoroughly clean the entire fuel system, including fuel pump, fuel lines, carb or fuel injectors, intake valves, and combustion chambers.