For at least 10 days this month, Chappaquiddick will be a one-ferry Island.

With the On Time III — the larger of the two ferries that run the 527 feet between Edgartown and Chappaquiddick — being hauled out of the water Oct. 20 for routine maintenance, Chappy Ferry owner Peter Wells is cautioning passengers about delays.

The On Time III will undergo her required Coast Guard exam and maintenance starting next week. Mr. Wells is estimating the work will take 10 days, but said it could take up to 20 days.

During that time, the smaller On Time II will shoulder the load. The On Time II can sometimes only hold two cars, Mr. Wells said, and he is asking residents that have an option to take their shortest vehicles on ferry trips during this period. He also asks people to remove their trailer hitch.

Because only one ferry will be running, Mr. Wells said ferry wait times could be up to three times longer than usual.

“You can help yourself and others by avoiding the normally busy times,” he said in an announcement.

“People will have to make do, and they generally do,” selectman Margaret Serpa said at the Edgartown selectmen’s meeting Tuesday.

To find out when both ferries are back in operation, call the ferry hotline at 508-627-6965, check the Chappy Ferry Facebook page, or text “chappy” to 69302 to receive Chappy text notifications.

This is Mr. Wells’ second attempt at getting the On Time III in for her check-up this fall; the original plan was to pull the boat out of the water Sept. 3. Mr. Wells said that last year, this was a quiet time for the ferry.

But huge ferry lines ruined that plan, and after just over a day out of the water the On Time III returned to service.