You have probably heard from a friend that he replaced the rubber bushings on his care with poly (polyurethane) bushings and it improved the automobiles suspension and steering system response and feel in his vehicle.
Well boats can take advantage of the same qualities of control with a very simple bushings swap. Polyurethane seems to be everywhere in the automotive marketplace and the folks at Hardin Marine , the industries leader in after market hi performance boat parts, is bringing it to the marine industry.
So what’s so great about poly? What does it all mean ? The durometer test is used to measure the initial hardness of the poly product. This basic test applies force in a consistent manner, without shock, providing a comparative number of the hardness (depth of the indentation) of a bushing or mass of poly material being designed for a certain application. Different products require different durometers (hardness and viscoelastic characteristics) to properly perform their intended function. The ideal durometer for a out drive will have a considerably higher durometer rating than its rubber counterpart, and that will make it resist crushing and compression much better than rubber.” resulting in a more stable outdrive. This stability is the key to your boats overall performance.
What you need to know when installing these new bushing. First, one of the most important things to understand about poly bushings is that they need to be pre-loaded. “Almost all polyurethane needs to be pre-loaded when installed. It needs to be placed under a little bit of stress on as much surface area of the bushing as possible. We call polyurethane bushings ‘free-flowing’ because the material wants to move in the path of least resistance, which is toward the places where it’s not contacting metal. In order to keep a poly bushing where it is supposed to be and performing how it should, the bushing and its trim ram are designed to create a pre-load on the bushing once properly installed. That way it’s going to stay in its location, not move around and get sloppy, and have increased longevity as the travel cycles. Greasing poly bushings is also recommended.