147, that applies to Yerushalmi but not Bavli. I think the Me’iri in his Hakdama to Avos explains that prefernce was given to the ‘Yeshivish Masechtos’ even in those days.
If you’ll notice the Gemara seems to easilly go off on a tangent when it comes to Taharos Sugyos. Since there was no Gemara set up for those Mishnayos they always jumped on the opportunity to stick it in wherever they could.