I'm unfamiliar with delamination issues after they switched over to thermo welding in 1987.
Could the ureathane coating have "blistered" away from the base fabric? Haven't seen this on a Maravia but other boats I have
If your boat is of the vintage you think it is, it will have a serial number stamped on the inside of the stern, the last two digits indicating year of manufacture
to this day they dont sell many boat in CA or OR.
My personal obervations suggest otherwise, Maravias are very well represented on the rivers I float in Oregon. Can't speak for CA rivers, haven't bagged one of those yet