Just to clear if you have a second solonoid its known as a slave solonoid,its purpose is to eliminate voltage drop on the long wire run from the ign switch,if you don't have a slave switch have a good electrical shop install one.when a solinoid just lightrely clicks but won't crank the starter then you jump from bat.terminal to "s"terminal and starter cranks its because of voltage drop,this will also cause arching of the contacts inside solonoid,replacing the solonid cures the problem but not the cause.If your into boats you can pick up a nice small waterproof slave at any mercruiser dealer. good luck
