Eliminating Engine Vibrations – Is a Strut Alignment the Answer?

2017 June 5
by Chris Brown

We recently worked on a 96-foot Ferretti yacht that had run aground and was experiencing considerable engine vibrations. Our field technicians with High Seas Yacht Service inspected the boat and found that the shafts were bent and one of the struts was bent and out of alignment. After pulling the props and shafts, we sent the shafts off to our machine shop, Straight Line Marine for straightening. Once the shafts were back in true, we sent them back to the vessel for re-installation after performing a full strut alignment on the vessel.

Strut alignment is often overlooked when trying to determine the cause of vibrations in a boat. All too often the first or second course of actions are shaft straightening or engine alignment when the root of the problem may lie in the struts. Struts can be out of alignment due to poor factory set-up or a hard grounding causing a bent or twisted strut.

Strut alignments are complex and require special tools and experienced mechanics. Once a strut is removed from the boat it is a major repair and should only be done by specialist in this field.

We begin the process with an optical scope alignment for precision measurements of the misalignment. In order to align the strut, it must be removed or dropped from the bottom of the boat. All strut bolts are removed and a considerable force is applied to break the bond between the strut and the hull. Proper equipment and safety are a major concern since some struts can weigh hundreds of pounds.

Once removed, the strut pad and hull pockets must be ground clean in preparation for installation. Extra jacking holes are drilled and tapped in the four corners of the strut pads to help with fine tuning adjustments. Once preparation is complete, the strut is hung back in its original place and the optical scope is once again used for precision alignment of the strut cutlass bearing.

When the strut is properly aligned, we use ChockFast to inject into the gap between the hull and strut to form a perfect fit with the bottom of the hull.

A strut alignment is typically a one-time project for any vessel unless it is driven hard aground. A properly aligned strut will free-up an engine to provide a smooth ride for comfort and higher speed with lower fuel consumption. For more details on performing a full strut alignment, click here.

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