Clogged vent is very likely cause. I've also heard of these same symptoms with a cracked distributor cap. Check inside the cap for moisture when this happens again.
It's always good to replace old parts, but there are checks to determine where the problem is and avoid removing good parts.
You should get a multimeter or a power probe-type tester to help isolate your problem. An HEI spark tester is also a good tool and has been very helpful for me.
Battery check; you should have at least 12.4V static, and the voltage should not drop below 10V during start cycle. If battery passes both tests then it is good and does not need to be replaced.
Alternator: Battery voltage should test approx. 13.5V with engine running. Anything below 13V indicates alternator needs to be replaced.
Spark: Use HEI tester to check for spark next time your problem happens. If you are getting spark then it is certainly fuel related. If no spark then work backwards from distributor to coil to ICM. This test is in Vol 24 (5.0 service manual) in documents section, see "testing thunderbolt V ignition" section. There is also a check for the coil so no need to guess. Let us know if you'd like help checking your systems.
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine