Stonehaven lifeboat was launched in the early hours of Thursday morning after a yacht broke down near Dunnottar Castle.
The RNLI crew manned the Jamie Hunter and headed out to the sailing vessel at about 4am.
The yacht was heading north under sail when the wind dropped at about 1am, and the two-man crew was unable to start their engine.
Concerns grew that the tide might pull the boats towards the rocky coast, with the coastguard calling out the Stonehaven lifeboat to come out and help.
After arriving on-scene and confirming the safety of the crew, RNLI crew mechanic Paul Sim was taken on board and assessed the situation.
He was able to get limited power from the engine.
This allowed the sailing vessel to be escorted into Stonehaven harbour just after 7am by the RNLI crew.
Speaking just after the call-out, helm Andy Martin said: “It was certainly an early morning pager call for our volunteer crew, and they quickly got to the scene.
“It had the potential to become quite dangerous for the sailing vessel, but Paul’s mechanical experience and expertise came in very handy.
“We are pleased to have been able to help and the situation worked out with everyone recovered safe and well.”