Mercury - Solenoid Switch Relay Up Trim System Component Marine-Grade Construction Number 898103T09. Overview. There's a certain feeling you get when your trim responds instantly that smooth rise of the bow, that familiar shift in attitude as the boat settles into the sweet spot. When everything works the way it should, you barely think about the components behind it. But every seasoned boater knows the trim system depends on a few critical parts, and a solenoid switch relay is one of them. The