2005 Kawasaki STx-12F Jet Ski Factory Service Manual., Page 141Get this manual
4-6 ENGINE LUBRICATION SYSTEM Specifications
Item Engine Oil Grade Viscosity Capacity Standard API SE, SF, or SG API SH or SJ with JASO MA SAE 10W-40 4.0 (4.2 US qt, with or without the filter) 5.0 (5.3 US qt, when engine is completely dry) Between upper and lower level lines (see text)