The crew of the Osprey was plucked to safety around 10 miles south west of Cape Wrath by the Coastguard helicopter based in Stornoway and flown to hospital.
The alarm was raised at around 6.35pm on Wednesday when the distress alert was sent from the boat, which was taking on water.
A spokesman for the Coastguard said: “Stornoway Coastguard sent the coastguard rescue helicopter to the scene and requested the launch of Lochinver RNLI all weather lifeboat to the incident ten miles south west of Cape Wrath.
“When the Stornoway Coastguard Rescue Helicopter arrived in the area they quickly located the vessel which was found within one mile of the distress alert position and still afloat.
“The three crew were alongside in a life raft and the vessel sank shortly afterwards.
“All three crew were winched into the aircraft and transferred to the Western Isles Hospital at Stornoway to be checked for hypothermia.”