The group won the license for the site, located 22km off the Dutch coast, following a tender in December, with a bid of €54.50/MWh, excluding transmission costs.
A spokesman said the consortium was seeking further investment in the project due to offshore wind requiring "substantial capital".
"The consortium of Eneco Group, Diamond Generating Europe, Shell and Van Oord is exploring options to attract additional investors in the Borssele III/IV project," the spokesman said.
"This is part of a planned assessment by the consortium on how to best fund the project and future offshore wind projects for the long term.
"Attracting solid additional investors allows each partner to free up capital to invest in new projects in future. We are in the energy transition for the long-haul and broad-based support will help continuity in the long-term," he added.
In March, MHI Vestas was announced as the preferred supplier for the project. It is set to deliver 78 V164 9MW turbines to the site.