Proper Boat Hose Sizing | Boating Magazine

Proper Boat Hose Sizing

Excerpted by Boating from the U.S. Coast Guard Boating Safety Resource Center website, uscgboating.org.

Federal Law
183.558 - Hoses and Connections

(a) Each hose used between the fuel pump and the carburetor must be "USCG Type A1" hose.

If a hose is used in the fuel line running between the fuel pump and the carburetor, the hose must be "USCG Type A1" and so labeled as required by 183.540. This requirement is applicable whether the fuel pump is engine mounted or mounted remotely from the engine, as permitted by 183.566.

This requirement does not apply to a tube used to detect fuel pump diaphragm failure.

To Comply With the Law
•A hose used between the fuel pump and the carburetor is "USCG Type A1."

Federal Law
183.558 - Hoses and Connections

(b) Each hose used -
(1) For a vent line or fill line must be:
(i) "USCG Type A1" or "USCG Type A2"; or
(ii) "USCG Type B1" or "USCG Type B2" if no more than five ounces of fuel is discharged in 2-1/2 minutes when:

(A) The hose is severed at the point where maximum drainage of fuel would occur,
(B) The boat is in its static floating position, and
(C) The fuel system is filled to the capacity marked on the tank label under Sec. 183.514(b)(3).
(2) From the fuel tank to the fuel inlet connection on the engine must be:
(i) "USCG Type A1"; or
(ii) "USCG Type B1" if no more than five ounces of fuel is discharged in 2-1/2 minutes when:

(A) The hose is severed at the point where maximum drainage of fuel would occur,
(B) The boat is in its static floating position, and
(C) The fuel system is filled to the capacity marked on the tank label under Sec. 183.514(b)(3).

The selection of the type of hose to be used in a fuel system is evaluated in accordance with the following:
(a) The boat must be in its static floating position as defined by 183.505. The fuel system is filled to the capacity marked on the fuel tank label as specified by 183.514(b)(3). Normally this quantity of fuel may fill the fuel tank to its topmost surface but will not fill the fuel tank fill or vent lines. Fuel is required to fill the fuel distribution line to the carburetor connection in order to determine the quantity of fuel that will leak in 2-1/2 minutes if a hose is severed.

Table IV shows the length of hose or tubing of various diameters, that if filled with fuel will contain five ounces. You will see that only a short portion of fuel fill or vent hose will require that hose to be "USCG Type A1 or A2"; Most fuel fill and fuel tank vent installations will permit the use of "USCG Type B1," but particular care must be taken if the fuel fill line and/or fuel tank vent line are run horizontally from the fuel tank connection. Any dips below the topmost surface of a fuel tank may cause a need for "USCG Type A1 or A2";

To determine what type of hose may be used for the fuel distribution line, it is necessary to:
(a) determine where, in the hose portion of the fuel line, maximum drainage could occur.
(b) cut the hose at the maximum drainage point. The intent is to cut the hose completely through and then support the hose at both sides of the cut at their original location.
(c) measure the fuel leakage from this opening in the fuel hose for a period of 2-1/2 minutes. If more than five ounces leaks, use "USCG Type A1." If less than five ounces leaks, you may use "USCG Type B1."

"USCG Type A" hose may be used for all hose portions, regardless of whether the installation proves that "USCG Type B" hose is acceptable. If "USCG Type A" hose is used, there is no need to test for five ounces of fuel leakage in 2-1/2 minutes.

TABLE IV - Length of Hose vs. Five Ounce Fuel Capacity
Note:
Table IV shows the length of hose or tubing of various diameters, that if filled with fuel will contain five ounces.

To Comply With the Law
•Are all fuel distribution lines "USCG Type A1"? If not:
Place the boat in its static floating position (see 183.505) Fill the fuel system to the capacity marked on the fuel tank label. Cut the hose portion of the fuel line at its maximum drainage point. Measure the fuel leakage in 2-1/2 minutes.

•If less than five ounces leaks, "USCG Type B1" hose may be used.

•If more than five ounces leaks, "USCG Type A1" hose must be used or the fuel line must be rerouted to comply.