Multiple Reciprocal Causation in Estimations

Hi

I am trying to analyze these estimations:
y1= y3 x1 x2 x3 x4 x5 x6
y2= y3 x1 x2 x3 x4 x5 x6
y3= y1 y2

Will 3SLS do the trick since there are two reciprocal causations?
Or if it's not possible, what should I do?

Thanks