The Tilton XLT Starter is a very reliable unit. It should spin the engine over every time you hit your starter switch. If it doesn't, you may need to replace the brushes.
This assembly has all four brushes pre-installed and pre-wired to a convenient drop-in plate. Simply unbolt the motor housing from the gear reduction housing (the main casting behind the mounting nose) to expose the old plate. Clean the carbon off the armature contacts, drop in the new plate, and reassemble.