13404-ZW5-003 Tensioner - Overview. The 13404-ZW5-003 Tensioner is a critical component within Honda marine engine systems, specifically supporting the balancer belt system. Its primary function is to maintain the correct tension on the balancer belt, which is essential for the efficient and reliable operation of the engine. By preventing belt slack and ensuring optimal belt alignment, this tensioner helps avoid premature wear and potential engine performance issues. Designed to fit factory spec