A majority of business owners have yet to make plans for the day when they'll need to hand the business over to someone else, according to a new survey.

The survey by Wilmington Trust found that 69% of owners of privately held businesses are unprepared to transition or sell their businesses, despite the fact that about half of such businesses are owned by baby boomers.

"As these business owners enter retirement age, a 'silver tsunami' of business sales is likely," the report said.

Asked why they haven't made succession plans, 51% of business owners cited market conditions and 61% said it is because they derive satisfaction from running the company, the report said.

The survey also appeared to identify some contradictions in how business owners view their preparations for the next generation of ownership.

"Moreover, although 89% of owners believe their business will survive without them because they have a business transition plan, only 55% have actually developed a formal business succession plan and just 49% have performed a business valuation, while only 48% are training or preparing successors to take over," the report said.

The report warned that lack of preparation could harm the return owners get on their business once they decide to sell.

"Owners who do not begin planning years in advance of a transition risk suffering 'the unplanned discount' of lower proceeds from a liquidity event," Stuart A. Smith III, a managing director in Wilmington Trust's family business advisory division, said in a prepared statement. "A positive business transition requires ample time and foundational work. This survey shows that for too many business owners that foundational work is not taking place." 

The survey, conducted online in September and October, focused on 1,007 owners of privately held U.S. businesses with at least $5 million in revenue.