Off My Dock: The Legacy of Dr. Dennis Throckle

The legend of Dr. Dennis Throckle never gets old.

February 7, 2017
The Legacy of Dr. Dennis Throckle
The Legacy of Dr. Dennis Throckle Tim Bower

My good friend Chuck Larson frowned as he idled up to the dock, one hand on the tiller of a 1975 Evinrude kicker he’d picked up at a rummage sale. The motor looked like new thanks to our short-season/freshwater environment, and its potential seemed worth $200, but I could tell by Chuck’s sour visage that the little blue-and-white outboard had not met his expectations.

“She idles fine, but when I throttle up she feels all boggy,” Chuck said. “Kind of surging or something. What do you think?”

I volunteered to take a test run, and I returned with a diagnosis for Chuck.


“I’ve never been to service school, but it sounds to me like the classic symptoms of a clogged Throckle filter,” I said with confidence.

“The Throckle filter,” Chuck said. “I’ve never heard of that.”

“When I worked at OMC, there was a run of trouble with the Throckle filter in a lot of these Evinrude motors. If it gets clogged, it restricts the flow through the exhaust port and you lose power. It’s not hard to replace, but there’s nobody around who still knows how to work on these old two-stroke outboards. Service techs who know about the Throckle filter have all retired. I’d take this motor to Evergreen Marine. They’ve been Evinrude dealers since we were kids. Insist that the problem is the Throckle filter, and get them to pull down the service manual from the shelf and look it up. They won’t find it on their fancy BRP service tablet.”


I first learned about the Throckle filter and its inventor, Dr. Dennis Throckle, in 1984 when I was hired fresh out of school as a writer in the Outboard Marine Corporation communications department in Waukegan, Illinois. After a few weeks, one of the old hands took me aside and explained that once in a while, an outboard owner would call the main OMC corporate number instead of the customer service line, and that the switchboard would often shoot those calls to our department.

“As the new guy, you are going to get those calls,” he said, “and a good way to settle down an unhappy customer is to sound confident that we can solve their problem. Tell them our motors are so reliable, there’s only one thing that could be wrong, and after you transfer them to the OMC service department, the customer should tell the tech they have a clogged Throckle filter.”

Later at lunch, this sage told me all about the late Dr. Throckle, or Dr. T as he was known in the OMC engineering labs. Some say his genius was discovered in Milwaukee by Ralph Evinrude, who knew him as the mysterious “fifth founder” instrumental in helping Bill Harley and William, Walter and Arthur Davidson start a motorcycle empire. Others said Throckle was farming outside Beaver Dam, Wisconsin, when he showed Carl Kiekhaefer how to fix a barn full of Thor outboards, and then he was spirited away to Waukegan by future OMC CEO Charlie Strang when he jumped the Mercury ship. The Throckle filter, I was told, was protected from Mercury by the most potent of patents and a pack of rabid attorneys.


Weeks later, I was chewed out by a red-faced customer service manager after I’d transferred my first call to his department. I was young and gullible but still savvy enough to keep my mouth shut. I realized I’d just been handed a gift by the late Dr. Throckle.


More How To