I have a friend who always buys cheap stuff. Anyways he traded me a three pack of those marathon blades ,they are junk. Thin kerf and made cheaply,I tried them on my jobsite saw framing houses and could not even stand them there . Gave one away and tossed the other two.
Thanks again for the replies.
Update FWIW: I tried sandwiching the blade between a pair of Amana 4" "blade stabilizers," and it didn't seem to change anything except that the blade took longer to spin down due to it being a heavier flywheel with the stabilizers.