HYANNIS - In the latest skirmish in the continuing battle between the Tisbury board of selectmen and the Steamship Authority, the port council yesterday backed a boat line plan to shift three summer trips from Vineyard Haven to Oak Bluffs.

The decision by the council, which advises the SSA board of governors, came over the bitter protests of council member and Tisbury selectman Thomas W. Pachico and fellow selectman Tristan Israel. The council voted 5-1, with Mr. Pachico dissenting and Nantucket member Nathaniel Lowell absent, to back the SSA plan.

The boat line board is slated to vote on the proposed ferry schedule at its next meeting, scheduled for Oct. 20 in Vineyard Haven.

The SSA board also has scheduled a workshop at 2 p.m. next Friday at the Hyannis terminal to discuss how a proposed $4 million rate hike for the coming year should best be allocated.

The Tisbury selectmen, meanwhile, are scheduled to meet boat line managers at 3:30 p.m. today at the Vineyard Haven ferry terminal to discuss town-SSA issues.

The schedule dispute is one of the latest developments in an ongoing conflict that has worsened in recent months between the Tisbury selectmen and boat line officials. Its roots lie in the standoff between the town and the SSA over Tisbury's decision not to use its ferry embarkation fee funds to pay for extra police assistance and traffic control near the Vineyard Haven terminal.

Now the discussion of which trips go to which Vineyard towns has sparked the anger of Vineyard Haven business owners, who anticipate Oak Bluffs merchants will benefit at their expense.

The Tisbury Business Association has gone on record opposing changes in the schedule. This past weekend, Tisbury taxi operators distributed flyers calling on Vineyard Haven businesses to fight any change.

Adding an extra edge to the issue is that Marc Hanover, the Vineyard SSA governor, owns the Oak Bluffs restaurant Linda Jean's. Mr. Hanover, who is chairman of the boat line board, has led the SSA over the past year in its disputes with Tisbury.

Yesterday in Hyannis, Mr. Israel wondered whether the proposed schedule change is payback to Tisbury for its disinclination to go along with the boat line. He said he hoped the SSA proposal was not punitive, adding: "That's sure what it feels like to us."

"This is more than fair," replied Mr. Hanover about the schedule. "I assure you that nothing is punitive."

The schedule change now recommended has in fact been scaled down from the original proposal, put forward at last month's boat line meeting.

Boat line managers initially suggested shifting more trips from Vineyard Haven to Oak Bluffs, including the 7:45 a.m. arrival of the ferry Martha's Vineyard, the first passenger boat coming off the mainland in the morning.

Mr. Lamson said yesterday the SSA dropped that idea because of the hardship it would impose on commuters from the mainland who depend on using the Tisbury Park & Ride lot off State Road in Vineyard Haven.

The revised plan calls for shifting two freight boats from Vineyard Haven to Oak Bluffs from May through October.

Also, from June 19 to Sept. 10, the passenger ferry coming out of Woods Hole at 7:30 p.m. would put in at Oak Bluffs rather than Vineyard Haven. The trip still would run to Vineyard Haven at the start and conclusion of the season.

Oak Bluffs port council member Robert Huss said he saw relatively little impact from shifting the trips. Mr. Huss said the freight boats involve mainly trucks, while the passenger boat coming out of Woods Hole at 7:30 p.m. would mostly carry Vineyarders returning to the Island after a day spent on the mainland.

But Mr. Israel said the boat also would carry passengers interested in traveling to the Vineyard as part of a summer evening's entertainment. He said they would be people interested in visiting restaurants and stores in Vineyard Haven before returning to the mainland on a later passenger boat.

If traffic congestion is the driving concern behind the plan, Mr. Pachico said, the SSA plan simply would shift the problem with the arriving boats from Vineyard Haven to Oak Bluffs. Passengers and automobiles would be coming off the 8:15 p.m. arrival in Oak Bluffs just as the town's nightlife would be getting under way, he said.

"To me, it's ludicrous," Mr. Pachico said. "It's causing problems on the other end."

Grating on the Tisbury selectmen as well was the way they said they learned of the proposed schedule change: indirectly and too late.

Mr. Pachico said the port council was getting its first look yesterday at the schedule change. Mr. Lamson disagreed, saying the council had received information about the change at its meeting early last month.

Mr. Israel said he did not learn of the change until he heard about a report that Mr. Hanover made to the Dukes County commissioners at their Sept. 14 meeting. The proposed schedule changes were discussed in detail at the SSA meeting the following day in Hyannis.

In the past, the selectmen said, SSA officials had met with town officials to discuss service changes in that particular town.

Mr. Israel also faulted the lack of time given to the Tisbury selectmen to react to the proposed changes, which he characterized as being put down the town's throat from on high.

But Mr. Lamson countered that the port council was created precisely to serve as a conduit of SSA information to the boat line's port communities. In that light, Mr. Pachico would be responsible for letting his fellow selectmen and townspeople know about potential boat line changes.

Yesterday's extended discussion about the proposed change in the Vineyard schedule stood in contrast to the almost total lack of discussion about an even more significant proposal on the Nantucket route.

The council voted 6-0 to back management's proposal to replace a passenger boat with a freight boat in the early and latter part of the season (mid-May through mid-June, and mid-September through mid-October). At those times, the Nantucket route will run three round trips with a passenger boat and six round trips with freight boats. Mr. Lamson said the move will allow the Authority to cut costs.

On the fall schedule, the Authority would run three round trips with a passenger boat and three round trips with a freight boat.