In 1988 Textron Marine was awarded the contract to develop a replacement for the 44' Motor Life Boat which had been in service with the Coast Guard since the early 70's. The first prototype was completed in 1990 and following two years of surf trials and evaluations, five additional, and improved prototypes were constructed and delivered to the Coast Guard for further evaluation. In 1997 the first production 47' MLB was accepted by the Coast Guard, and since then well over one hundred have been produced. The ultimate goal is to have approximately 200 in service.
The 47' motor lifeboats are 47 feet long, have a beam of 14 feet, and draw 4.5 feet of water. Their displacement is 20 tons at full load and they have a compliment of 4. The 47' MLB can accommodate up to 5 additional passengers/survivors. They have a top speed of 25 knots, and a cruising speed of 20 knots. Their maximum cruising range is 200 nautical miles. They have a 100-ton towing capacity.
The 47' MLB is of an all aluminum construction, is capable of operating in 20' breaking seas and winds of 60 knots, and can survive impacts at three times the force of gravity. The 47' MLB is self righting, and can return to an upright, operational configuration within 10 seconds, whether "pitch-polled" (rolled fore and aft) or rolled into swells (rolled across the boat's beam.) In addition, the MLB is self-bailing and its machinery is not subject to operational interruption, even while inverted. The boat can be operated from both an exposed bridge (offering better visibility in rescue situations) or from the enclosed pilothouse (to limit crew fatigue during extended surf operations.) To mitigate the pounding effects associated with surf operations, the 47' MLB incorporates shock absorbing crew seats. These seats feature 360 degrees of rotation, lap belts, armrests, and lumbar supports. The survivor compartment is also watertight and climate-controlled, for survivor safety, comfort, and medical recovery.
The 47' motor lifeboats are powered by two Detroit Diesel engines, producing 870 horsepower combined. Propulsion is provided by two shafts fitted with fixed pitch screws.
Focused on inshore search and rescue operations, the 47' MLB's are equipped with SSB (single side band) HF and VHF radios for communications, as well as a VHF-FM, RAYCHART 620 electronic chart system, and GPS/LORAN system for electronic navigation. The 47' MLB is also equipped with an SPS-69 navigational radar.
The 47' motor lifeboats are not armed.