Before we get to the SOLAS requirement for MOB marker rope length, lets start with the requirements of the following:
Stowage requirement for lifebuoys
As per SOLAS Ch III, Regulation 7:
1) Lifebuoys shall be:
A) so distributed as to be readily available on both sides of the ship and as far as practicable
on all open decks extending to the ship’s side, atleast 1 shall be placed in the vicinity of stern
B) so stowed as to be capable of being rapidly cast loose, and not permanently secured in
any way
2) At least one lifebuoy on each side of the ship shall be fitted with a buoyant lifeline equal in length to not less than twice the height at which it is stowed above the waterline in the lightest seagoing condition, or 30 m, whichever is the greater.
Also read : Thermal Protective Aid on-board
3) Not less than one half of the total number of lifebuoys shall be provided with lifebuoy self-igniting lights, not less than two of these shall also be provided with lifebuoy self-activating smoke signals and be capable of quick release from the navigation bridge. Lifebuoys with lights and those with lights and smoke signals shall be equally distributed on board the ship and shall not be the lifebuoys provided with lifelines.
4) Each lifebuoy shall be marked in block capitals of the Roman alphabet with the name and port of registry of the ship on which it is carried.
Do note here that lifebuoys with smoke signals are the ones used as MOB markers on vessels. These are located on each side of the bridge wing (as SOLAS requires minimum 2 of these on each vessel). Now we will get into the requirements for lifebuoys.
General requirements for lifebuoys
Every lifebuoy shall:
A) have an outer diameter of not more than 800 mm and an inner diameter of not less than 400 mm
B) be constructed of inherently buoyant material. It shall not depend upon any air compartment which depends on inflation for buoyancy.
C) be capable of supporting not less than 14.5 kg of iron in fresh water for a period of 24 h
D) have a mass of not less than 2.5 kg
E) not sustain burning or continue melting after being totally enveloped in a fire for a period of 2s.
F) be constructed to withstand a drop into the water from the height at which it is stowed above the waterline in the lightest seagoing condition or 30 m, whichever is greater, without impairing either its operating capability or that of its attached components
G) if it is intended to operate the quick release arrangement provided for the self-activated smoke signals and self-igniting lights, have a mass of not less than 4 kg
H) be fitted with a grabline not less than 9.5 mm in diameter and not less than 4 times the outside diameter of the body of the buoy in length. The grabline shall be secured at four equidistant points around the circumference of the buoy to form four equal loops.
Requirements for lifebuoy lights
Lifebuoy self-igniting lights shall:
A) be such that they cannot be extinguished by water.
B) be of white colour and capable of either burning continuously with a luminous intensity of not less than 2 cd in all directions of the upper hemisphere or flashing (discharge flashing) at a rate of not less than 50 flashes and not more than 70 flashes per min with at least the corresponding effective luminous intensity
C) be provided with a source of energy for a period of at least 2 h
D) be capable of withstanding the drop test.
Requirement for lifebuoy smoke signals
Lifebuoy self-activating smoke signals shall:
A) emit smoke of a highly visible colour at a uniform rate for a period of at least 15 min when floating in calm water
B) not ignite explosively or emit any flame during the entire smoke emission time of the signal
C) not be swamped in a seaway
D) continue to emit smoke when fully submerged in water for a period of at least 10 s
D) be capable of withstanding the drop test
E) be provided with a quick release arrangement that will automaticaly release and activate the self-igniting light connected to a lifebuoy having a mass of not more than 4 kg.
Since an MOB marker consists of both, a self igniting light & a smoke signal as well, hence it had to comply with all the above given SOLAS requirements.
SOLAS requirement for MOB marker rope length
This has been a topic of long debate. For clarification, SOLAS DOES NOT MENTION ANYTHING ABOUT ROPE LENGTH, ITS DIAMETER REQUIREMENT IN MOB MARKER OR ITS BREAKING STRENGTH OR ANY OTHER CHARACTERISTIC.
The confusion is because most manufactures mention the rope length and breaking strength in their manual for MOB marker buoys. Hence in general, a rope of length about 4m and diameter 8mm. It is the responsibility of the manufacturer to make the rope strong enough to not break while bearing the weight of the smoke and light unit.
