After 41 years in business, Boulder Electric Motor Co. owner Bill Thielman, 89, and his son, Billy, 64, are calling it quits, a move that is sending hundreds of their Boulder County customers into deep mourning.

The elder Thielman, a Montana-born petroleum engineer, started the motor company in 1975 and gradually turned it into a bustling, nearly invisible hub for dirty-hands enthusiasts, do-it-yourself folks who couldn’t bear to throw a motor away if it could be fixed.

But the company’s reputation for problem-solving, custom repairs and its deep affinity for every kind of motor, capacitor, belt, gear and shaft soon grew. Eventually, the 7,500-square-foot machine shop behind the quiet storefront on East Walnut in Boulder was humming. Its mechanics could fix a vast array of electric things — from tiny motors in the tape drives for Louisville’s Storage Technology Corp. to giant locomotives in underground mines in the high western foothills.

In 1977, the Thielmans opened a store in Fort Collins. They had a large base of customers who quickly learned that motors that are well-cared for and refurbished from time to time can last a lifetime.

When the Boulder Public Library’s heating and cooling system began to fail, the library turned to Boulder Electric Motor Co. to help it revamp the internal workings of the aging system, allowing it to operate again at much less than a new system would have cost.

Though low-key, the company became something of an industrial powerhouse, working on high-stakes, custom projects for such major clients as CU’s Muenzinger Auditorium, Western Electric and IBM.

“I’ve been through every back door in town,” said Boulder Motor’s former shop foreman, Cliff Cowan, who joined the firm out of high school in 1978 and is now helping the Thielman’s shut it down.

But 17 months ago, the company’s longtime bookkeeper, Arlene Flannery, retired. It would take months to replace her, and once the books were caught up and inventory balanced last month, it became clear the company had lost nearly $200,000.

Two weeks ago, the Thielmans opted to close.

“Our market has changed,” Thielman said. “They build electric motors so well now that they last forever.”

Since word began to filter out that the venerable institution was closing, customers have been stopping in — some to cash in on the 40 percent going-out-of-business sale, but mostly to reminisce about the goodwill the shop has generated over the years.

For customers such as Jeff Eigner, who lives outside of Niwot, the closing of the shop is a loss.

“The place is a gold mine,” Eigner said. “I’m a double “e” (electrical engineer) and a bit of a do-it-yourselfer. I stumbled upon them when I was looking for help fixing a water pump I had years ago. My father-in-law died recently, and he was a master at holding onto parts in case they could be used and fixing things that someone else would throw away.

“Their shop brought that back to me. Everyone is bemoaning the fact that they are closing.”

As the younger Billy Thielman chats with a customer and friend late on a recent weekday afternoon, his astonishingly youthful father talks about the end of this particular industrial era on East Walnut.

“We helped a lot of people and made a lot of friends,” the elder Thielman said. “I figure Billy had about 1,000 customers who came to him. But we grew to be quite huge and if you miss a step, you’re in trouble.

“I’m sorry it has to end this way,” he added. “But I’m glad that people liked it.”