Crew member Jamie Forrester and his friend, and boat owning partner, were approaching Dunbar Harbour shortly before 6pm on Monday.
Coming back from an afternoon sail with their families, the engine on their 26ft yacht Kerry Girl failed to respond.
They sailed to a safe location to drop anchor.
Dunbar’s RNLI crew was called out to assist with the incident, however attempts to fix the problem failed.
The UK Coastguard tasked the crew at 6.15pm and launched an inshore lifeboat ten minutes later.
They set up a tow and guided the yacht into the harbour.
The coastguard stood down the crew at 6.47pm.
A spokesman for Dunbar RNLI said: “Even with a well-maintained engine incidents can happen but Jamie and his friend did the right thing by dropping anchor, making sure their yacht was in no immediate danger and requesting help.”