Cowes Harbour Commission say the work will take place Tues-Thurs, but Isle of Wight council say the Floating Bridge will be out of action for five days.
Measures that 'may be introduced' in Portsmouth include vehicles registered before 2006 or diesel vehicles registered before 2015 faced with a charge to enter the city.
Islanders who regularly drive through Portsmouth may wish to take part in this survey calling for views on a possible £8 per day clean air zone charge in the city.