The boat builder behind some of the Sydney to Hobart's most memorable finishes has been rocked by accusations of sabotaged relationships and shoddy craftsmanship in a director feud that spilled into the Federal Court.

Acrimonious infighting erupted at McConaghy Boats - whose website describes it as the iconic race's "most successful builder" behind yachts such as Wild Oats XI, Alfa Romeo and Loki - after it was sold to a Cayman Islands-based company, MC².

Wild Oats XI on Sydney Harbour in December 2018. Credit:AAP

Emails revealed in court proceedings that have since been dismissed by consent show the one of the directors of MC², Graham Porter, describing another, Jonathan Morris, as a "poison ... that must be removed".

Mr Morris originally ran McConaghy with co-owner Mark Evans before it was bought by MC² in an investment deal with foreign company Tiger Yacht Management, chaired by Mr Porter, in 2014.