(A) EACH FUEL TANK SUPPORT, CHOCK, OR STRAP THAT IS NOT INTERGRAL WITH A METALLIC FUEL TANK MUST BE INSULATED FROM THE TANK SURFACE BY A NON-MOISTURE ABSORBING MATERIAL.

Unless a metallic fuel tanks has built-in means for supporting and holding the fuel tank in place, a non-moisture absorbing material must be between the fuel tank surface and the support, chock, or strap. The non-moisture absorbing quality of the material is necessary to prevent localized corrosion of the fuel tank that might occur if moisture was trapped at the support-tank interface for a prolong period of time.

The following table lists some material that appear to be suitable and some that should be avoided. Care should be taken to avoid abrasive combination of materials even though it is not a mandated requirement.

Basically, this requirement provides for the isolation of the metallic fuel tank from potentially moisture ladden support system and also from abrasion by the supports, chock, or strap.

FUEL TANK ISOLATION MATERIALS

NOTE: This list is not limited to the material to be included. They are to establish the intent of the regulatory requirements prohibiting moisture absorbing materials.

Coast Guard, DOT

Manufacturer Requirements

§183.550 Fuel tanks: Installation

(a) Each fuel tank must not be integral with any boat structure or mounted on an engine.
(b) Each fuel tank must not move at the mounting surface more than one-fourth inch in any direction.
(c) Each fuel tank must not support a deck, bulkhead, or other structural component.
(d) Water must drain from the top surface of each metallic fuel tank when the boat is in its static floating position.
(e) Each fuel tank support, check, or strap that is not integral with a metallic fuel tank must be insulated from the tank surface by a non moisture absorbing material.
(f) Cellular plastic must not be the sole support for a metallic fuel tank.
(g) If cellular plastic is the sole support of a non-metallic fuel tank, the cellular plastic must meet the requirements of §183.516 (b) or (c).
(h) Each fuel tank labeled under §183.514 (b)(8) for installation aft of the boat’s half length must be installed with its center of gravity aft of the boat’s half length.
[CGD 74-209, 42 FR 5950, Jan. 31, 1977, as amended by CGD 81-092, 48 FR 55737, Dec. 15, 1983]