502 mag Mercruiser EFI w/180 hours

Was on the lake all day with no problems. Then when it came time to
get off the lake the engine would start then immediately shut off.
Then it would start and once I tried to give it some gas it would shut
off. During this time I also noticed a sucking/hissing coming from the
flame arrestor when the engine would shut off . I eventually got the
boat started and it ran fine and I was able to reach full throttle
with no problems.

The next day, the boat started up easy and ran fine all day, until I
decided to go back to the launch. I then again experienced the same
problems as the first day.

My dad thinks it's the fuel filter. I just had the boat serviced 20
hours ago and a new fuel filter was put in. What else could it be? I'm
just confused because the problem seems to be intermittent.

Any help would be greatly appreciated.