ROCHESTER — This is the time of year when spring weather drives some enthusiasts into their garages to build a Great American River Racer to take down the Mattapoisett River in a grueling race against each other and against the elements.

But there are fewer competitors now than there used to be. The chairman of the Great American River Racers estimates that there will be about 50 boats in this year’s race, compared with 70 only a decade ago or so.

Organizer Gary Stopka said, “It’s the X-Boxes, the PlayStations. It’s a different type of world.”

So the organization held a two-hour open house Saturday at the fire station on Hartley Road, hosted by Chairman Arthur Benner. People could get a good look at the boats and meet the racers without getting in the way in the commotion of race day. About 20 people showed up, some of them with their children, who they are trying to get interested in building and racing a river boat.

Tom Richardson of Mattapoisett was there with his 12-year-old daughter Summer. He was delighted at the boats, and that says something as he is the host of the New England Boating Show on NECN weekly, as well as the editor of New England Boating and New England Fishing magazines.

“When the kids are old enough they can get into boating. It’s a bonding experience,” Richardson said.

He is impressed by the legacy of these boats. “They’re traditional. It’s really cool,” he said.

Building and racing the boats is often a family affair. Dan Gagne of Rochester was there with his daughter Cori, 9, son Blake, 10, and father David Gagne.

One cannot go out and buy one of these river boats, unless someone wants to sell one or will be building it for you. It is usually necessary to build your own. So the local boaters have put together building drawings that are easy to follow and result in a plywood  boat that’s about $250 or a fiberglass one that’s about three times that, and very sturdy to handle the rocks in the river.

The Great American River Racer, according to the write-up that accompanies the drawings, ”is quite possibly the easiest and most inexpensive boat that can be built.”

At just over 15 feet and up to 18, the boats take a pounding as they are launched for practice runs on the river.

The boats are distinctive but familiar. They are designed to look a lot like canoes, and are almost as fast as racing canoes.

They have distinctive features such as a sloping transom. The boat is shallow and flat bottom, so as to navigate the obstacles such as the two low bridges that have racers lying down in their boats to make it underneath.

Builders and racers such as Gary Stopka, who is trying to make it to 50 consecutive races (44 so far), say that if a boat cannot make it to the halfway mark in the 12-mile race in two hours, which is a spot on Wolf Island Road near the Mattapoisett town line, they will be hauled out of the water and end their racing day.

The competition can be friendly, but it is always intense enough to keep the racers coming back year after year.

The river racers can be contacted at 508-996-4593.

Follow Steve Urbon on Twitter @SteveUrbonSCT