PORTLAND – Another border battle is brewing between Maine and New Hampshire, and it has nothing to do with which state owns the island on which the Portsmouth Naval Shipyard sits.

Maine lawmakers are considering a bill that would end the practice of allowing New Hampshire residents to snowmobile free of charge across the state line. The two states are the last in the nation to allow the practice.

The Maine Snowmobile Association is lobbying hard for the bill because the state is missing out on revenue from New Hampshire riders. The Maine Legislature’s Fish and Wildlife Committee voted unanimously for the bill on April 11, but the bill has yet to be debated on the floor.

If it were approved, Mainers would pay $47 to register in New Hampshire, while New Hampshire residents would pay $60 to register here.

Gene Chandler, speaker of the New Hampshire House of Representatives, said the proposal threatens cooperation between the two states.

“We don’t want another border war,” Chandler said. “Our feeling is if we can’t get along between the two states amongst the residents and allow us each to go snowmobiling, I don’t foresee us getting along on much else.”

The Maine Snowmobile Association estimates that 17,000 New Hampshire residents cross the line to ride in Maine each year, based on a 1997 survey. Getting even half of them to pay would raise $510,000.

“We have a user-pay system and it’s only fair that all the users pay,” said Rep. Matt Dunlap, D-Old Town, one of the sponsors of the bill. “New Hampshire has always gotten the better end of that deal.”

It doesn’t help that Maine State Police are cracking down on Mainers who live along the border and register their cars in New Hampshire to save money.

Some Mainers believe the same thing is happening with Massachusetts residents registering their snowmobiles in New Hampshire to ride for free in Maine.

The Maine Warden Service investigated this winter and reported that out of 431 sleds checked in western Maine, only 34 were registered in New Hampshire. The riders of 14 of the 34 sleds were from other states.

But while both states could gain registration revenues from ending reciprocity, they could lose money, too. Everyone has an opinion about how much, but no one has much data.

The Maine Snowmobile Association’s 1997 study estimated 40 percent of New Hampshire snowmobilers rode in Maine in 1995-96 and spent about $3.1 million. But if Maine starts charging, many New Hampshire snowmobilers swear they’ll stay home or travel to Vermont or Quebec.

Snowmobiling is important to the economies of both states. The snowmobile industry brings an estimated $260 million into Maine’s economy and $355 million to New Hampshire. There are an estimated 6,000 miles of groomed trails in New Hampshire and 12,000 miles in Maine.

As the dispute has become more heated, each state has questioned the other’s statistics, strategies, motives and trail grooming. Each swears that ending reciprocity will hurt the other more.

Even the jokes have a hard edge.

“They’re never neighborly. I mean, they’re trying to steal the damn shipyard,” said Bob Meyers, the executive director of the Maine Snowmobile Association. “I don’t know what it is, maybe the ‘Live free or die’ thing.”

Paul Gray, chief supervisor of New Hampshire Bureau of Trails, counters that “Maine’s the vacation state, but they make it harder and harder to vacation there.”