Fuel Systems

Equipment Standards

If cellular plastic (foam) is to be used to encase a metallic fuel tank, it must as a minimum comply with the properties and tests specified in the regulation.

If the foam used for encasing a metallic fuel tank is to be counted as part of the flotation required for boats under 20 feet in length by Title 33 CFR 183 Subpart F, it may be required to comply with additional properties and tests as follows:

* If the foam is in the engine compartment and low in the bilge it must be resistant to gasoline and oil, and must not absorb water.

a. If the encasing foam is:

1. in the engine compartment, and
2. BELOW a height of 12 inches above the lowest point where liquid can collect in that compartment

   then, the foam must not lose more than five percent of its buoyancy or dissolve after being immersed in any of the following liquids for 30 DAYS (instead of 24 hours) at 23ºC (80ºF):

1. Reference fuel B of ASTM D-471
2. No. 2 reference oil of ASTM D-471
3. Five percent solution of trisodium phosphate in water.

   * If the foam is high in the engine compartment it must be resistant to gasoline vapors.

b. If the encasing foam is:

1. in the engine compartment, and
2. ABOVE a height of 12 inches above the lowest point where liquid can collect in that compartment

   then, the foam must not lose more than five percent of its buoyancy or dissolve after being immersed in a fully saturated gasoline vapor atmosphere for 30 DAYS at 38ºC (100ºF).

   * If the foam is not in the engine compartment but is low in the bilge of the boat it must still have some resistance to gasoline and bilge cleaners.

c. If the encasing foam is:

1. outside the engine compartment, and
2. below a height of 4 inches above the lowest point where liquid can collect in that compartment

   then, the foam must not lose more than five percent of its buoyancy or dissolve after being immersed in any of the following liquids for 24 hours at 23ºC (80ºF).

1. Reference fuel B of ASTM D-471
2. Number 2 reference oil of ASTM D-471
3. Five percent solution of trisodium phosphate in water.

Suppliers of foam should advise buyers if their products comply with these specifications.

NOTE: The 4-inch and 12-inch heights are measured when the boat is in the static floating
position. Refer to 183.505.

TABLE 1 - Foam Requirements If Used For Both Fuel Tank Encasement And Flotation

A boat builder may choose to accept a foam supplier’s certification to these requirements. Alternatively, these tests can be performed by the boat builder or a laboratory. There is special equipment involved and careful measurements required in accordance with laboratory techniques. It is recommended that all referenced standards and specifications be obtained and that the tests be performed in accordance with the detailed instructions contained therein.

Regardless of who performs the tests, the boat builder is responsible for compliance.

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