Debut goals from Hull’s club-record signing Abel Hernandez and Mohamed Diame, facing his former club, were cancelled out in the second half by Enner Valencia and then Davies’s turn-in.
Hernandez, who arrived from Italian side Palermo on transfer-deadline day, marked his debut for the hosts with a brilliant headed goal from Ahmed Elmohamady’s cross in the 39th minute.
Ecuador’s World Cup striker Valencia, another Premier League new boy, equalised for West Ham five minutes after the restart with a long-range strike that stunned the home fans into silence.
A familiar face then came back to haunt the visitors when Senegal captain Diame, making his Hull debut after joining from the Hammers, took advantage of sloppy defending to curl past Adrian after 64 minutes.
The celebrations were short-lived, with defender Davies accidentally turning in Diafra Sakho’s shot three minutes later to give Sam Allardyce’s 13th-placed team a fourth point in as many games.
“It was a bit hair-raising for me when you go down twice and probably don’t deserve to, especially the second one when Mo Diame scored having just joined them,” West Ham manager Sam Allardyce told Sky Sports.
“But we showed great character, I did not think there was much between the two teams. We respect the point. It was a very good performance by the team who will only get better as they get to know each other more.”
Both teams started the game sluggishly and it took Hernandez, keen to show the home fans why he commanded a 10 million pound ($16.23 million) fee, to bring the game to life.
The Uruguayan striker directed a powerful header into the corner of the visitor’s net to open the scoring and then nearly doubled his tally five minutes later but his fierce left-footed strike from 25 yards rattled against the crossbar.
Strike partner Nikica Jelavic headed in the rebound but he was correctly adjudged offside.
West Ham weathered the storm to half time and came out after the restart with greater impetus. It did not take long for Valencia to level the score with his first goal on his first start for the London club.
The Ecuadorian, who scored three goals at the World Cup, made some space for himself outside Hull’s area and curled a thunderous effort into Allan McGregor’s top corner off the underside of the bar.
It appeared to be a case of one-upmanship between the league’s two new South American strikers.
Diame then punished his former employers after collecting a sloppy throw-in from West Ham left back Aaron Cresswell to drive into the area and side foot into the corner to give the hosts a 2-1 lead.
The second-half had one more twist though when a tame Sakho shot rebounded off the shins of Hull defender Davies to level the score.
West Ham might have stolen all three points in the last minute when Valencia nearly scored again but his header hit Hull defender Michael Dawson and bounced off the crossbar.
Steve Bruce’s side are 10th in the league with five points, and the Hull manager said he could reflect on an encouraging display in a breathtaking second-half where both teams created good chances.
“The two goals, the first one in particular from their new striker, you just have to hold your hands up – it was a wonder goal and it made for a really good night of football. It was open, end-to-end and all credit to West Ham, they played some good football today,” Bruce said.
(Reporting By Sam Holden, editing by Alan Baldwin and Clare Lovell)