GUTTENBERG (AP) -- Elevated fuel prices have increased the cost of pleasure boaters' pleasure but have not forced them to forgo it.

Gas- and diesel-guzzling houseboats and cabin cruisers, which travel about a mile per gallon at cruising speed, remain in use at levels similar to those prevailing before the recent run up in fuel prices, according to marina operators, Mississippi River lockmasters and boaters themselves.

The weekly price of regular-grade gasoline, which peaked at $4.11 per gallon on July 14, averaged $3.81 per gallon on Aug. 11 -- $1 a gallon more than last year's average price, according to the federal Energy Information Administration.

Despite that 35 percent increase, pleasure boat traffic on the Mississippi River at Guttenberg "is pretty close to normal, maybe down a little bit from last year," said Lockmaster Marvin Althoff, who tracks boat traffic through Lock and Dam 10.

"If you can afford the boat, you can probably afford the gas," Althoff said, referring to purchase prices easily exceeding $100,000 for large, late-model vessels.

"A lot of boaters have a big investment in their boats, and they are still going to be out here having fun, even if they have to spend more at the gas pump," said Dan Rogers, owner of the Coralville Lake Marina, tucked into the lake's southeast corner just above the dam.

"Boat sales declined when gas hit $4 a gallon, but the gas dock has been as busy as usual," Rogers said.

Sales of both boats and gasoline have been down this summer at Hartwick Lake Marina on Lake Delhi, "but I can't really say it's because of high gas prices," said marina employee Deb Luensmann.

Since the lake's chronically high water receded in July, boating activity has been "pretty much back to normal," she said.

Higher fuel prices "have not slowed us down much," said Dick Cornish of Marion, who with his wife, Sherry, spends about three days a week on their 44-foot houseboat docked at Winegar Works marina just above Lock and Dam 10 at Guttenberg.

The 10-ton boat, powered by twin 454-cubic-inch V-8 engines, gets about 0.7 miles per gallon going upstream and about 1.1 mpg coming downstream, he said.

"We don't leave the marina as much as we did, we take shorter trips, and we load more people on board when we go," Cornish said.

Joel Wikner of Denver said he's "not really feeling the pressure" of higher fuel prices -- even though his 50-foot houseboat gets less than a mile per gallon.

"We don't waste any fuel, but it's not really affecting our lifestyle," said Wikner, who docks his 13-ton craft at the Winegar Works marina.

Nor have high fuel prices detracted from Lynn and Diane Moller's enjoyment of their 31.5-foot Sea Ray -- technically an ocean fishing boat but used by the Waterloo couple as a pleasure cruiser.

With its twin 260-horsepower engines, the boat consumes about 20 gallons of gas per hour at its 28 mph cruising speed, but the Mollers said they generally travel at a rate between 7 and 9 mph.

"We are out to enjoy the scenery, not to get anywhere in a hurry," said Lynn Moller.

The Mollers, who also dock at Winegar Works, typically leave their slip at noon Saturday and don't come back until Sunday afternoon.

They anchor over a favorite shallow sandbar, where they swim, grill out and marvel at the brilliance of stars in an otherwise unlit sky. Sometimes as many as 30 boats anchor on that same sandbar, replacing solitude with sociability, Diane Moller said.

The Mollers said they can't imagine fuel becoming so expensive that it keeps them from enjoying their weekend river lifestyle.

Duane Riley of Sun Prairie, Wis., who docks his 46-foot houseboat at Winegar Works, said high fuel prices have limited his travels but not his enjoyment of his weekend retreat.

"Probably 15 to 20 miles is all I've done this year, but we still come almost every weekend. It's like having a house on the river," Riley said.

Bill Veren of Marshalltown, who docks his 40-foot Sea Ray cruiser near Riley's houseboat, said he runs his boat as often as ever but on shorter trips and at reduced speeds.

"We usually just idle out and back. We go pretty easy," he said.

Norm Delphey, who with his brother Fred runs the Delphey Brothers Marina in Harpers Ferry, said he can imagine a price that would discourage many boaters.

"I think fuel at $5 a gallon would start to keep a lot of boaters home," he said.

The marina has sold 4,000 fewer gallons of fuel than it had last year at this time, but the decline has much more to do with high water than high fuel prices, Delphey said.

"Boating conditions on the Mississippi River were unfavorable until July 1, and a lot of our customers are from Waterloo and Cedar Rapids, and many of them had their own high water problems to deal with," he said.

Since July 1, when river levels became suitable for fishing and sandbar parties, boat traffic has returned to normal levels, Delphey said.