my boat is leaking water any advice what to check.

[fish player]

I have a inboard out board motor mercury motor with a mercruiser alpha one out drive. so far I checked the bellows look like there new I drop and picked up motor to check bellows the look good checked the clamps around bellows they where tight I also checked the shift cable below it looked good the clamp was broke on it I replaced it with a other clamp but still leaked water.put the plug in and filled the inside of the boat with water just below the starter I did not see any water leaking out I also checked the water lines in the boat they look good I removed the motor cover at the lake I could not see where the water was getting in any advice