Registration number 3818
Status Replica


Function Fighting Vessel
Subfunction Torpedo Boat
Location Portsmouth
Vessel type Motor Torpedo Boat
Current use Museum based
Available to hire No
Available for excursions No


Builder Boathouse4, Portsmouth
Built in 2017
Hull material Wood
Rig None
Replica definition Operational Replica
Number of decks 1
Propulsion Motor
Number of engines 1
Primary engine type Diesel
Boiler type None
Boilermaker None


Breadth: Beam
8.50 feet (2.59m)
2.25 feet (0.69m)
Length: Overall
45.00 feet (13.72m)


CMB4R is a fully operational replica of a Coastal Motorboat. The original batch of Coastal Motor Boats (CMB’s) were designed and constructed in 1916 by John I Thornycroft at Platt’s Ayot at Molesey on the River Thames. The War Department’s specification was for a fast, shallow-draught boat, capable of passing through a minefield and then delivering an 18-inch Whitehead torpedo. Boats of this type were used in raids on Zeebrugge and Oostende but, most famously, in 1919 on the White Russian fleet in the port of Kronstadt. On this daring raid, the cruiser “Oleg” was sunk for which Commander Augustus Agar and the boat involved (CMB 4) were awarded the Victoria Cross. “Coastal Motor Boat” was a “camouflage” term for the boat, so as to not give away its true purpose. The development of these boats was really a “great leap forward” in the way of thinking about fast, hydroplaning boats. The techniques and technologies used in the MTBs and MGBs (and other boats) of the 1930s and 1940s owe a great deal to the pioneering work used in the CMBs.

Key dates

  • 2016 Funding grant awarded by the Chancellor's LIBOR fund for the construction of the replica
  • 2017

    Construction begins at Boathouse4

  • 2023

    Vessel launched and afloat for the first time in June, with the first completely successful sea trial completed in September. Max recorded speed 36.4 kts

  • 2024

    Further sea trials in April extended the top speed to 39.2 kts

Own this vessel?

If you are the owner of this vessel and would like to provide more details or updated information, please contact

More like this

CMB 4 - starboard bow

National Historic Fleet, built 1916 by Thornycroft, J I & Co Ltd, Hampton

MTB102 sailing as part of the ADLS 70th anniversary fleet, May 2010

National Historic Fleet, built 1937 by Vosper, Portsmouth

CMB331- the entrance

Registered, built 1941 by Thornycroft, J I & Co Ltd, Hampton

View of MTB71 and a 20mm AA gun Credit NMRN

Registered, built 1942 by Vosper, Portsmouth