Determine the Stiffness of Marine Hoses

The vibration of a boat's engine led to a requirement that when metal tubing, like a fuel line, is connected to the engine, it must be connected with flexible hose. These hoses have to be checked regularly, including every time you fuel your boat. The stiffness, or lack of flexibility, in these hoses is a characteristic examined as part of the U.S. Coast Guard's approval process that certifies these hoses can be used aboard your boat.

Look at the hose. On the side of the hose, you will see a notice of U.S. Coast Guard Approval followed by an approval number. Following the USCG approval number will be a series of letters and numbers that describe the hose flexibility. There are four letter designations, A1, A2, B1 and B2.Inspect the hose, paying close attention to the clamps or end fittings, since these are the most likely locations for a leak. Read the letter/number designation. If the letter is "A," this describes the hose's resistance to fire. "A" is more fire resistant than "B." "A" hoses have to be used at fuel pumps and carburetors.

Look at the number in the letter/number designation printed along the length of the hose. Type 1 hoses are more impermeable and stiffer than Type 2 hoses. This means that:An A1 hose is more fire resistant and isn't prone to bleed fuel through the skin of the hose.A B1 hose is less fire resistant than an A1 hose, but isn't likely to bleed fuel through the surface of the hose, unlike an A2 hose. The B1 is stiffer than an A2.An A2 hose is more fire resistant, but more prone to bleed fuel through the surface of the hose, and thus is not as stiff.A B2 hose is less fire resistant than an A1 hose and as likely to leak as an A2 hose.