Treat them right, and they’ll take care of you and your boat.
After a 27-foot cruiser sank at its dock, investigators couldn’t figure out where the water had come from. When the boat was raised, they found that all the seacocks were closed; there had been no heavy rains recently; and the boat’s bilge pumps had been operating, though the battery was dead from trying to keep up with the inflow of water. Eventually, the surveyor spotted an outdrive shift bellows that seemed a bit loose. The hose clamp that was supposed to hold it in place was still there and appeared to be serviceable. It wasn’t until the surveyor started to remove the clamp that he noticed it was completely rusted in half on the side opposite of the screw.
We find a lot of problems in the BoatUS Marine Insurance claim files caused by hose clamps that failed: exhaust leaks, gas spills, and sinkings. Don’t take hose clamps for granted — the safety of your boat depends on them.
Use Good Ones
Clamps should be made completely of 316 stainless steel by a reputable company. Some clamps have screws that are made of cheap steel and rust easily. If the screw rusts, the clamp fails. Running a magnet over a clamp can tell you if there is any non-stainless steel, but unfortunately that can’t always tell you if there is any lower quality stainless used in the manufacture. Companies such as Ideal Tridon and AWAB are known for making suitable clamps if they are marine grade and not for automotive use. The best clamps, such as those made by AWAB, use smooth non-perforated bands, which prevent the inevitable corrosion in the slotted-type clamps. The rounded solid bands also prevent your clamps from acting like a cheese slicer on your hoses. Don’t cheap out and buy clamps from the local auto parts store. Cheap hose clamps are not good, and good hose clamps are not cheap.
Use Clamps That Fit
A clamp that’s too big leaves a long, sharp metal tail just waiting to slice the next errant finger or catch on a wire. A clamp that’s too small may not have enough threads holding it closed and could fail right when you need it.
Install Them Right
Clamps should be installed so that about a quarter-inch of hose is visible between the band and the hose end, and so that the band is completely seated on the barb of the fitting to which the hose is attached. Note that the Coast Guard doesn’t require double clamps anywhere on recreational vessels. The American Boat and Yacht Council (ABYC) requires them in only two places — fuel fill hoses and exhaust systems. But both the USCG and ABYC standards are minimums. Below-waterline fittings, including stuffing boxes, should always have two clamps installed if at all possible. Keep in mind that a hose fitting has to be long enough to accommodate two clamps, plus a quarter-inch space between them, otherwise the second one can damage the hose.
Tighten Them Just Enough
Most boaters are a little fuzzy as to how tight a hose clamp should be. Too loose, and you’ll have a leak; too tight, and the hose clamp will damage the hose and cause premature failure. How to get it just right?
A few years ago, Craig Senovich, an engineer at Tridon, did an informal test for Seaworthy to find out how much torque an average person could muster on a hose clamp. Craig gathered a few coworkers and, using a sophisticated measuring device, invited everyone to crank their hardest on a hose clamp using a nut driver (similar to a screwdriver, but less likely to slip). The average person could produce about 37 inch/pounds (interestingly, using gloves nearly doubled that figure). That number happens to be very close to the specifications for a clamp in the 5/8- to 1 1/2-inch range. When a ratchet was used, the hose clamp ended up over-tightened.
Lesson: Avoid the ratchet. Use a screw or nut driver and don’t be afraid to hand-tighten unless you’re built like a linebacker — then you’ll need to use a proper torque wrench.
Assume the clamp-inspection position and give your hoses a firm pull (best done out of the water) — it’s better to have the clamps fail now than when you’re underway or the boat’s on its own. Keep in mind that any corrosion is likely to be on the bottom of the clamp where water collects. This is often the hardest place to look, but a small dental mirror and a flashlight can make the job easier. Any corrosion, kinks, or other damage means their life is over — replace them.