16404-ZX2-000 Spacer Throttle Body - Overview. The 16404-ZX2-000 Spacer Throttle Body is an essential Honda marine engine system component crafted to create a precise distance or separation between connected parts in the throttle body assembly. Its primary function is to ensure proper alignment and spacing within the throttle body system, supporting smooth engine operation and reliable performance. Designed specifically for Honda marine engines, this spacer plays a critical role in maintaining t