The Coast Guard had to rescue three men Monday after their boat overturned while they were trying to recover the boat of three missing fishermen off the North Shore.

The rescued boaters sent an alert to the Honolulu Fire Department about 8:35 p.m., reporting they were sinking and abandoning ship before being abruptly cut off, the Coast Guard said.

An MH-65 Dolphin helicopter crew had to be diverted from the search for the three fishermen to respond to the distressed boaters’ alert, sent via an emergency position-indicating radio beacon.

The MH-65 Dolphin helicopter crew located the three men off Laie, hoisted them aboard and flew them to Haleiwa Boat Harbor. A fourth man swam to shore.

One of the four was treated by emergency responders for hypothermia, the Coast Guard said. No one else was hurt.

The boaters’ 30-foot recreation vessel Makanani capsized and sank while they were trying to tow in the 20-foot Iwa, which had been carrying the three missing fishermen, the Coast Guard said.

The Iwa boaters — Jensen Loo, Clint Oshima and Derek Tomas, all 30 — left Haleiwa Boat Harbor at about 5:45 a.m. Sunday and planned to return that afternoon at about 5, the Coast Guard said.

A friend reported them missing at about 8:20 p.m. Sunday. Friends said the boaters had sent a text message Sunday morning, saying they had caught an ahi. Friends also said the boat had been used to land several 150-pound ahi in the past.

During Monday’s search the Coast Guard spotted the Iwa overturned about 25 miles off Haleiwa Boat Harbor.

On Tuesday the Coast Guard continued searching for the missing fishermen with an MH-65 Dolphin helicopter, an HC-130 Hercules airplane and the cutter Kiska. A Navy helicopter also assisted in the search.

Anyone with information that might help locate the three missing men is asked to call Sector Honolulu Command Center at 842-2600.