There were 75 entries in 2014, which was the first race of the resurrected multisport challenge, previously run two decades before.
Organisers had tried to broaden interest by introducing a five-person format to go along with individual and 2-4 person team racing. They also offered to supply two-person kayaks.
However, Stoneman said this did not bring in any bites. "People talked about it, but no one was committed to it to give us the money."
Costs were $450 for a solo competitor, and between $595-795 for the teams.
Stoneman said they will now look ahead to 2016, "when we can meet our target numbers well in advance of our deadlines".
"We've got a new marketing team coming on board. Spread the web wider.
"We'll definitely be making sure next year's a biggie."
He has also had discussions with Coast to Coast race director Richard Ussher, as he took over the position in 2015 from the race's iconic founder Robin Judkins, who had sold the rights to the event to Queenstown's Trojan Holdings in 2013.
Ussher was also dealing with a decline in numbers for the 32-year-old event, which has made alterations in the past two years such as different team formats and changing the finish to New Brighton pier.
Stoneman said in a competitive market, they can learn from what others are doing.
"Our thanks to DoC staff who have helped develop this event, to iwi for their great support and Visit Whanganui and Mars Petcare for their continuing financial input and support.
"To our stage sponsors we thank you and look forward to 2016 when we have fantastic numbers that will give this event the much needed boost to bring it back into the NZ multisport fray."