First boat need some help troubleshooting an issue i had on the water yesterday

i own a 2002 bayliner 175 capri with the 3.0 mercruiser i/o motor and i took it out in swlf water for the first time yesterday and the boat was running smooth and started just fine and we were cruising at like 20 mph for like 20ish min and didn’t make it too far out but we decided to just stop and relax and i cut the motor which i probably shouldn’t have done but i did… and then i went to start it back up and it wouldn’t start for nothing!!!! it was acting like it was out of gas and i opened up the tank it it was still pretty full with plenty left to use and we tried and tried to get it started and nothing i was bumping the throttle like the manual says to do an i was squeezing the primer ball and it wouldn’t get gas to it and wouldn’t get firm so we had to get towed back to land.

i go out this morning and the boat started right up the first time!!!! the primer ball was firm like it had gas in it and it was running smooth again with no problems and it idled for 30 min without shutting off so i am so confused on what i would look for to prevent this from happening again.

again its my first boat so im still learning so bare with me