Update: my battery was indeed low on water.

Everyone, do yourself a favor and if you have a wet cell battery, set a reminder on your phone to check the water level every month or two. I haven�t checked mine in about 2 months and poof.

Lesson learned.

If the plates were exposed, significant impact to battery performance/service life resulted.
Note from my earlier post that you should never use 2 12V batteries in parallel as a "solution" unless you just want to make a stupid move and end up replacing batteries more often than necessary. Your choice on that one.

If you move up to something in the lower 24V class (like the mentioned ~70# thrust models) you can probably do just fine with two smaller deep cycle batteries (Group 24) that would be a very reasonable compromise on weight & reserve power. I see no need for two Group 27 batteries on a 17' aluminum boat.