Not everyone can swing a new boat, so what about retrofitting a Seakeeper? Johnstone says the gyro has to sit on “fairly substantial” structure. MJM installs stringers to accept the Seakeeper, but many boats will need additional support, adding complexity and expense to the job. Placement is also an issue: A Seakeeper is heavy—models range from 550 to almost 4,000 pounds, plus the additional weight of extra structure and ancillary gear. It doesn’t have to be mounted on the centerline from a functional standpoint, but centerline-focused weight is a factor in maintaining proper trim, said Johnstone.
In most retrofits, the Seakeeper can be tied into existing stringers, said Brook Stevens, regional sales manager at the company. Sometimes the stringers have to be sistered to get the right span for the mounts; this is figured out on a case-by-case basis, he said. Once the support structure is built, the Seakeeper—with a rotor that lives in a vacuum-sealed sphere that pivots fore and aft, supported by a sturdy steel cage that also holds the hydraulic active-control cylinders—can be secured either via metal plates glassed inside the stringer and tapped to receive mounting bolts or via tapped saddles that fit over the stringers and are glued in place with Plexus or another high-tech adhesive. Every Seakeeper installation is a custom job that should be carried out by authorized technicians, said Stevens. When planning a retrofit, contact the company first, he added. Engineers there can provide advice, and a list of certified installers. “We try to get involved in every project,” Stevens said.