A 6m fibeglass boat with two POB reported engine problems on a return trip from Whale Island to Whakatane.  The boat proceeded under reduced power and anchored off Whakatane Bar.  Sea conditions were good with 8kt NNW wind and 1m swell.  However, the tide was very low and the bar was shallow and there were breaking seas on the bar.  Whakatane Rescue was tasked to assist the boat and towed it over the bar to the boat ramp.