47-foot Motor Lifeboat

The 47-foot MLB is the standard lifeboat of the United States Coast Guard (USCG). The 47′ MLB is the successor to the 44′ MLB.[5]

A USCG MLB in the surf zone off the coast of Morro Bay
Class overview
Name	47′ MLB
Builders	Textron Marine
Operators	United States Coast Guard,Maritime Search and Rescue (Mexico)
Preceded by	44-foot motor lifeboat
Cost	$1,214,300[1]
In service	1997–present
Planned	c. 227[2]
Completed	227[2]
Active	227
General characteristics
Displacement	18 t (20 short tons)[3]
Length	14.6 m (47 ft 11 in)[3]
Beam	4.27 m (14 ft 0 in)[3]
Draft	1.37 m (4 ft 6 in)[3]
Propulsion	2 × Detroit Diesel 6V92TA DDEC-IV engines, 435 hp (324 kW) each[3] 1,500 liter (373 usable imperial gallons) fuel capacity [3]
Speed	25 knots (29 mph; 46 km/h) maximum 22 knots (25 mph; 41 km/h) cruising[3]
Range	200 nmi (370 km) cruising[3]
Complement	34 persons, 4 crew, 30 passengers[3][4]
Armament	1 × M240B machine gun (optional)[4]

An MLB ready for deployment at Motor Lifeboat Station Morro Bay, California

At Station Chatham where the new 47-foot boat would draw too much to get over the bar, the 42-foot Near Shore Lifeboat was designed to replace the 44' MLB. [6]

The 47′ MLB is designed to weather hurricane force winds and heavy seas, capable of surviving winds up to 60 knots (110 km/h), breaking surf up to 6 m (20 ft) and impacts up to three G's.[3] If the boat should capsize, it self-rights in less than ten seconds with all equipment fully functional.[3]

The boat's hull and superstructure are constructed entirely from 5456 marine grade aluminum.[3] Designed with a hard chined deep "V" planing hull,[7] the 47′ MLB exceeds its hull speed. The frame is composed of 17 vertical bulkhead frames, each of which is welded to the deck and hull, and five of which are watertight.[7]

Employing "fly-by-wire" control systems,[8] the boat can be operated from four different locations: two from the enclosed bridge, and two amidships from an open bridge.[3] Because of the “by wire” system the boat is controlled by joysticks instead of wheels.

Situated less than 1 ft (30 cm) above the water line are recessed retrieval wells,[8] allowing for easier recovery of persons and jetsam, and easier boardings.[3] A watertight survivor's compartment is equipped for comprehensive first aid.[8] It is situated at the combined center of rotation of the ship.[8] if needed a light machine gun can be fitted at the front of the vessel.