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Q: Your insurance company requires a survey prior to renewing your marine policy, and the surveyor reported that most of the hoses need to be replaced. How often should you replace your boat’s hoses, and what is the best hose to use?

A: I recommend that all cooling-system hoses be changed at a maximum of four years after installation, regardless of their external condition. There is a lot going on inside the hose that may not be immediately obvious on the outside.

The hoses are exposed to constant heating and cooling cycles, oil and grease from their close proximity to the engine, and coolant breakdown, as well as ozone damage. Abrasion damage where hoses are routed too close to and tucked beneath components cannot always be seen until the hoses are removed for replacement.

On suction and exhaust hose, look for soft, gooey or spongy surfaces caused by oil contamination. Bulges and swelling will be readily apparent. Heat damage results in hardened and cracked hose covers, while abrasion- damaged hose appears scuffed or gouged on the cover. Although not totally destroyed, the integrity of the hose is severely compromised. Be sure to correct the cause of the abrasion after replacing the hose. Ozone damage shows as tiny, parallel cracks in the hose cover, even though there is no hardening.

There are several different types of marine hose, and the application will dictate which hose to use when replacing.

Fuel hose must be Coast Guard certified and is rated for fire resistance and fuel permeation. Type ratings are A1, A2, B1 and B2, which will be clearly marked on the hose every 12 inches along with the manufacturer’s name and date of manufacture. Type A hose must pass a 2.5-minute fire test, while Type B isn’t required to. The number 1 or 2 represents the permeation rating, Type 1 hose being 1/3 as permeable as Type 2. Fuel distribution and return lines on gasoline-powered inboard and sterndrive boats should be A1, while fuel fill hose is typically A2. More information regarding fuel hoses is provided by the American Boat and Yacht Council ( in section H-24 of its standards, which should be required reading for anyone working with marine fuel systems.

Wet exhaust hose must comply with SAE J2006 or UL1129 standards and must be labeled as such. This means the hose is temperature-rated at 1,100 Fahrenheit for two minutes. The hose is flexible and resistant to heat, cold, abrasion, antifreeze and oil. Engine exhaust hose won’t kink or collapse under suction if the raw water strainer becomes clogged. It is at minimum two-ply, wire-reinforced, heavy-wall rubber hose. Other, more costly materials can be used in exhaust hose construction, based on the required temperature rating desired. According to ABYC section P1.7, “every exhaust hose connection shall be secured with at least two non-overlapping clamps at each end to produce a secure, liquid- and vapor-tight joint.” Good advice to follow.

Seawater intake hoses are connected to fittings below the waterline (engine cooling water, air conditioning suction line, head intake) and as such must be the best you can purchase. Even a slight leak at a through-hull can quickly sink a boat. Although I am unaware of any written standards, accepted practice is to use engine exhaust hose or equivalent, as intake hoses are on the suction side of the plumbing and are prone to collapse when strainers clog, contributing to rapid engine overheating at the very least.

Cooling system hose that circulates engine coolant must resist kinking, heat, antifreeze and oil. A heavy-wall, two-ply rubber hose is recommended. For tight bends, use wire-reinforced hose. A premium black automotive heater hose or blue silicone hose, both rated to meet SAEJ20 standards, will work well.

The best hose is only as good as the installation. Provide for smooth bends without kinks and with easily accessed clamps. Try to rotate clamps so that you can check the tension screws without being a contortionist, and install chafe protection wherever possible. Use high-quality all-stainless clamps, not the inexpensive part-stainless type sold in auto supply stores. A good marine clamp also will have rounded band edges to prevent cutting into the hose. AWAB brand clamps are the best I have used and can be reused numerous times (