West coast ferry operator CalMac said there was no easy solution to the demand for transport to the islands.
A spokesman said: “Ferry traffic is very much as we would expect at this time of year, with the popular peak sailings very busy, but with adequate space at other times.
“The Western Isles routes are no different from other popular routes across the network, but unfortunately there is no quick fix to provide additional, reservable capacity on these busy days.
“We would encourage people who are not tied to weekends to consider travelling at other times and during busy periods, it would help everyone if customers advised us as timeously as possible of changed plans and cancellations to maximise what space we do have on the most popular sailings.”
He added: “We have agreed with the Outer Hebrides tourism body to carefully monitor and review all reservations on routes to the Outer Hebrides to see if there is any traffic which can be transferred away from key sailings.”
The huge Hebridean visitor surge often means last minute visitors have difficulty in finding a bed during the peak season.
The issue of the lack of space on ferries was been raised by Western Isles Council repeatedly.
Councillor Roddie Mackay, who has previously crossed swords with CalMac over the issue, said the situation was “unbelievable”.
Mr Mackay added: “We are all aware of the economic impact as it blocks tourists coming to the islands.”
Mr Mackay said it was also a serious problem for islanders who could longer travel when they need to.
He was affected when he could not get his car onboard the MV Isle of Lewis.
He said: “It’s not only about how many tourists are not getting on to the islands, but also how many locals not getting away.
“Simple access and exit to and from the islands for locals is really, really difficult and very frustrating during the summer.”