Hose Clamps for Boats: Below the Waterline

The lowly hose clamp is a very important item on a boat. Pay close attention to clamps below the waterline when looking at a used boat.

The lowly hose clamp is a very important item on a boat. Pay close attention to clamps below the waterline when looking at a used boat.

You’re buying a new or used boat, and while inspecting the engine space and below the floorboards you’re pleased to see new hoses on the through-hulls: engine intake, head intake, sink drains, etc… But something doesn’t seem right. Then you notice that there’s only one hose clamp on each through-hull when there should be two!

Yes, just like the old Rodney Dangerfield two-bagger joke, two hose clamps are required on every through-hull, just in case!

West Marine Advisor has a good article on choosing the right hose for the application, but also recommends using double hose clamps on hose-to-pipe connections below the waterline for extra security. So does the American Boat and Yacht Council (ABYC) in their standards for Seacocks, Through-hull Fittings, and Drain Plugs (H-27).

There are two types of hose clamp — the familiar worm-style  and the T-bolt hose clamp. T-bolt clamps are used in applications with high pressure, heat, vibration, or other severe requirements, like exhaust systems. T-Bolt clamps are much stronger and have a 360-degree clamping surface.

All hose clamps should be made of high-grade (316) marine stainless. Marine-grade stainless steel has a higher nickel content to resist corrosion. The more popular manufacturers are AWAB, Shoreline, Tridon, and Ideal, to name a few.

The T-bolt hose clamp is used in applications where there's high stress, vibration, or heat, as in an exhaust system.

The T-bolt hose clamp is used in applications where there’s high stress, vibration, or heat, as in an exhaust system.

Poorly made and cheaper hose clamps will often have adjusting screws of a lower-grade steel, and these screws can begin to corrode fairly quickly, compromising the effectiveness of the clamp and eventually the safety of your boat. As Practical Sailor says, it’s good policy to take along a strong magnet when you go shopping for hose clamps.

Now you know:

  • which hose to use
  • how many hose clamps to use below the waterline
  • what type of clamp to use — worm-style or T-bolt
  • how to tell the difference between high-quality and low-quality clamps

… so you can have peace-of-mind that the boat you’re buying is properly outfitted.

In order to accommodate two clamps over the hose barb, you’ll have to make sure to use hose barbs that are long enough to give both clamps some gripping surface. One more tip: Use a little liquid soap on the hose barb to be able to slide tight-fitting hoses onto the barb.

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