We investigate the viscosity dependence on concentration and molecular weight of semiflexible polyelectrolyte sodium carboxyrnethylcellulose (NaCMC) in aqueous salt-free and NaCl solutions. Combining new measurements and extensive literature data, we establish relevant power laws and crossovers over a wide range of degree of polymerization (N) as well as polymer (c) and salt (c(s)) concentrations. In salt-free solution, the overlap concentration shows the expected c* proportional to N-2 dependence, and the entanglement crossover scales as c(e) proportional to N-0.6 +/- 0.3 in strong disagreement with scaling theory for which c(e) proportional to c* is expected, but matching the behavior found for flexible polyelectrolytes. A second crossover, to a steep concentration dependence for specific viscosity (eta(sp) proportional to c(3.5 +/- 0.2)), commonly assigned to the concentrated regime, is shown to follow c** proportional to N-0.6 +/- 0.2 (with c**/c(e) similar or equal to 6) which thus suggests instead a dynamic crossover, possibly related to entanglement. The scaling of c* and c(e) in 0.01 and 0.1 M NaCl shows neutral polymer in good solvent behavior, characteristic of highly screened polyelectrolyte solutions. This unified scaling picture enables the estimation of viscosity of ubiquitous NaCMC solutions as a function of N, c, and c(s) and establishes the behavior expected for a range of semiflexible polyelectrolyte solutions.