https://www.scag.com/OPManuals/FreedomZ/2013SFZOPMAN/SFZ48_Book_03322.pdf
remove blower housing, top engine cover, & clean with shop vac, cheap paint brushes etc. remove dirt, grass, etc. from all areas, including engine cooling fins. this is why i suggest using a shop vac to loosen crud up vacuum it up, do not use water. clean underside of deck & check blades for sharpening, let us know if this helps.
do not know if this is your manual above:
https://www.scag.com/manuals.html