World's Largest Underground Testing Facility
Headquartered in Hudson, Wisconsin, Konrad Marine is a manufacturer of stern drives and their replacement parts. The company produces commercial and pleasure stern drives for both gas and diesel applications.

Konrad Marine knows that whether you operate your boat only on weekends in the summer or if you earn your living running a charter service, every hour of operation counts. That’s why Konrad Marine supplies stern drives that are durable, dependable and perform.

How committed is Konrad Marine to providing the very best stern drives? Consider this. In 1995, the company completed construction on the world’s largest underground marine testing facility. This is where our products are stressed, pushed and proven.

The entire oval is built below grade to allow year-round testing without the threat of freezing (Wisconsin has long, cold winters).

The manufacturing bays of Konrad can be expanded right over the top of the in ground testing facility to allow for additional floor space.

The Konrad Marine Testing Oval is constructed of 30.05 centimeters (12 inch) reinforced concrete walls with a center observation area of .274 square meters (295 square feet) with three .6 meter by .6 meter (2’ x 2’) windows that are 2.54 centimeters (one inch) thick to withstand the water pressure. And also ensure safety from any accidental breakage. This facility means our testing and research into propulsion science never stops.


The empty facility has an approximate weight of 450 tons, but when filled with some 80,000 gallons of water, the facility weighs more than 750 tons.