In this paper we consider the use of single carrier modulations combined with frequency-domain equalization schemes (SC-FDE) in doubly selective channels where the channel variations are due to both phase noise and carrier frequency offset (CFO). Since carrier phase variations within the block duration can compromise significantly the performance of block transmission techniques. We propose an iterative receiver with joint symbol detection and phase-noise decision-directed estimation where we approximate the a posteriori phase noise probability density function by a weighted sum of Gaussian functions.