My inbord 5.0 240 HP when is cold start and run fine.After 10-15 idle it runs rough and then quits. Wont start for 2 hrs sometimes longer.Rebuilt carburator last year,new sparkplugs.l can not find problem.Please help !

Sounds like the motor is loading up with fuel. Run the boat until it stalls, and check the plugs. Are they wet with fuel? If so, make sure the choke butterfly is fully open when the motor is warm. Clean the pivot points and linkage with carb cleaner. Beyond this, you should have the carb checked/rebuilt by a trained tech.

if the carb was rebuilt it may not have had the proper float level set. It does sound like either a stuck choke or too much fuel entering the intake. This engine has an electric choke pull off so check the wiring to this device also.

This sounds like a carburetor problem. First check that the choke is correctly set and opens fully once the engine is up to temp. If so, check the idle screw settings (two screws) in fact you might have to replace them. If that does not help, replace the float valve and set it slightly lower than it is now.