Since you mention a backer board I assume your tear out is at the exit point. To me this would imply that the backer is not tight enough against the...
Glenn, I had the wrong number. Correct model number is 113.29901.
This thread may help. Besides Grandpa's 1950 Emerson I had a 1970's "113." contractor. I added a decent fence, PALs, machined pulleys and a link belt. I also wrapped a 90# bag of Redi-crete in plastic and tossed it in the base for ballast.
I could get the blade very well aligned at 90 degrees but, as with nearly all contractor format saws, bevel cuts were a challenge.