Mechanical Safety Tip of The Week

As I cruised through the Miami Boat Show last week I spent a lot of time looking at very fine details on a lot of boats. One of the thoughts that always enters my mind when I look at steering systems in particular is what might happen if what we in engineering circles call a single point failure were to occur on a high speed boat's steering system. You get the idea, blasting through the water at 50 mph and suddenly the steering lets go. The steering system on your boat is one of the few areas where a single ...

16th February 2010.
By Ed Sherman

As I cruised through the Miami Boat Show last week I spent a lot of time looking at very fine details on a lot of boats. One of the thoughts that always enters my mind when I look at steering systems in particular is what might happen if what we in engineering circles call a single point failure were to occur on a high speed boat’s steering system. You get the idea, blasting through the water at 50 mph and suddenly the steering lets go. The steering system on your boat is one of the few areas where a single point failure could occur, and it could have some pretty wild results. Prevention is easy, but you need to be aware of a basic fact about “Nylock” nuts used to hold the steering system of your boat together. In the photo below you can see four of these nuts in place.

What you’re looking at is a steering link between two large outboard engines and the ends of the two hydraulic rams that control the steering and synchronization of the two engines as they turn from side to side. In this case, particularly with the steering link, if the nylock nut were to rattle off at high speed and the bolt the nut was holding place were to rattle out of place you might end up in a situation where the two engines are pointing in different directions! I don’t think I need to elaborate on what that might be like at 50 mph. The point here is two-fold. Remember that nylock nuts are only intended for use ONE time. Secondly, always look carefully at them to make sure the bolt threads actually protrude all the way through the nut and the nylon ring that acts as the locking device. Often, the bolt isn’t quite long enough to achieve this and that means there is actually no protection against the nut backing off the threads. Details, details, but these are the sorts of things guys like me are trained to look at. Just passing this on, and yes I did find several brand new boats where the locking section of these nylock nuts were not engaged due to the use of bolts that were too short!


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Ed Sherman

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Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.
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