I have a 1996 ChrisCraft 21' with a 5.0 OMC Cobra fuel injected engine with 350 hours. The engine starts right up when the engine is cold but after I run the boat for 30 minutes to a few hours ill dock it or beach it for a little while. When I go back to start it up after 10-60 minutes, I have to crank it for 10-15 seconds for it to start. Just wondering what this may be. Thank you in advance