We present a search for a Higgs boson decaying to two W bosons in pp collisions at s√=1.96  TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0  fb−1 collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200  GeV/c2, and determine upper limits on the production cross section. For the mass of 160  GeV/c2, where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section.