Mulvey spoke on the phone with Bolt - who is in Europe - on Monday night, according to a report in The Daily Telegraph.
While the move has been heavily criticised by some in the Australian football community, it appears closer than ever with the Mariners and those in Bolt's negotiating team having signed a confidentiality agreement.
“There’s a confidentiality agreement in place which we must abide by but that in itself is probably the biggest indicator of where it’s at,” a club spokesman said.
“They’re very serious, they really want this to work, so they want to be very respectful to the Mariners and the A-League and give this the best go.
“That is all that can be said at this time.”
It is understood that the likely six-week trial is still a few steps away, with Football Federation Australia yet to fully support the move.
The FFA are said to have been initially skeptical of the move, which included the governing body contributing around $900,000, but Bolt's marketing power has drawn in sponsors who are willing to partly fund the deal, lessening FFA's financial burden.
“If he is good enough FFA would be willing to assist the Central Coast Mariners in financing the deal,” A-League boss Greg O’Rourke said.
“While not ruling out using FFA funds, it is more likely that we would be facilitating corporate and commercial partnerships.”
The potential move has generated headlines around the world, simultaneously alerting other clubs internationally who could be interested in bringing in the 100-metre world record holder, which could see them outbid the Mariners, but for now the deal seems closer than ever.