I’m not familiar with a
Newport 31, but that sure looks like some fairing where a bolt-on
keel ends and meets up with a ridge on the
hull (maybe leading to the prop shaft exit?). In and of itself, not extremely concerning to my eye.
But… someone familiar with these specific
boat may be able to tell you if it’s indicative of anything deeper. For a the standard production “flexy”
hull, it would seem unsurprising that there would be enough movement there to crack a rigid fairing compound, so maybe it’s just a case of using something with a little compliance. But if this is an unusual thing to see for these
boats, it could mean the keel has loosened, and would warrant more investigation.