A helicopter and two lifeboats saved a fishing vessel taking on sea water in gale force winds about 35 miles off the north Norfolk coast.
Coastguards at Great Yarmouth were alerted to the incident at about 0110 GMT by a gas rig supply boat.
Fishing vessel Fruitful Harvest III was in difficulties with four people on board, the crew told coastguards.
The fishing vessel had lost power on two pumps and a third was struggling, coastguards said.
A helicopter brought a new pump and the vessel was towed back to Grimsby in Lincolnshire in 60 knot winds.
Coastguards said the weather was very poor throughout the operation, which took several hours to complete.
Winds were 45 knots gusting to 60 knots and the sea swell was about six metres.
"Rescue helicopter 128 transferred a pump to the fishing vessel via a steel line, as weather conditions were too dangerous to lower a winchman," coastguard watch manager Mario Siano said.
"The crew of the rescue helicopter managed to drop the very heavy and unwieldy pump on the back of a fishing vessel in nearly 70mph winds."