Mercury Marine is the world’s largest manufacturer of marine engines. Boating NZ recently visited its primary manufacturing facility and Global HQ in Fond du Lac. Story by John Eichelsheim.

Fond du Lac is a modest-sized Wisconsin town located at the southern end of Lake Winnebago, the largest lake within that state. With the lake water beginning to freeze and snow falling steadily for both days we were there, there wasn’t a whole lot to see, but I got the impression it’s a pleasant enough town to live and work in.

Fond du Lac is home to Mercury Marine, a division of the Brunswick Corporation. It’s where Mercury has its world headquarters and main manufacturing plant, and while it’s no longer the only game in town, with more than 2,500 employees it remains one of Fond du Lac’s main employers.

The Mercury plant was the reason Anthony Brown (AB), Marketing Manager for Mercury Marine ANZP, myself, and a pair of Australian marine journalists were in Fond du Lac. AB had arranged a two-day guided tour of the facility that included access to most of it. He’d even secured permission for us to take photographs and video in parts of the plant, a privilege that’s apparently seldom granted.

Mercury takes security seriously, with guards at the gates and passes issued for visitors (and their cameras). It’s impossible to miss the Mercury Marine plant, which sprawls over a several blocks on both sides of a main road. To call it big is an understatement. I quickly understood why we needed two days to see it.

This plant manufactures Mercury outboards, from 90hp to 600hp, and Mercruiser sterndrives. And it really does manufacture engines, not just assemble them – from casting the blocks, powerheads and manifolds to precision machining components: pistons, shafts, gears and pinions, fastenings and more. Mercury’s comprehensive corrosion protection is said to be the best in the industry.


Making extensive use of industrial robots, with more robot lines continually coming on stream, and benefiting from massive investment in R&D and new plant, the Mercury facility at Fond du Lac is not only the largest, but also the most advanced such operation in the world.

As a first-time visitor to Mercury Marine HQ at Fond du Lac, I found the scale of it rather difficult to comprehend at first, but the facility is split into different divisions, or campuses, spread over the main site and its satellite premises nearby. Some of these divisions are in separate buildings, but the bulk of the plant is under one vast roof.

The factory has grown steadily over the years with older parts of the plant housing what Mercury calls its ‘legacy’ manufacturing, which includes Mercruiser, Mercury’s L4 four-cylinder outboard range, L6 Verado, and some of its propeller casting operation. However, even the legacy plant has undergone regular updating and renewal over the years, and the oldest lines and processes are ‘modern’ by most standards, with many of the lines including robots. Mercury Marine is in the process of steadily replacing its legacy lines with more modern plant.

Most recently Mercury Marine added 22,000ft2 (2,044m2)of factory space, which was still being fitted out during our visit, investing over US$200 million to boost manufacturing capacity. This investment has been in response to elevated demand for Mercury engines.

The gap between supply and demand was compounded by the company’s decision to retrench when Covid struck in 2020, which seemed a prudent move at the time. But like many marine companies, Mercury misread the situation. Demand for Mercury engines exploded during the pandemic and the company soon found itself scrambling to supply customers. Mercury Marine has since made a huge effort to increase manufacturing capacity, re-open plants, and restore staffing levels, with staff numbers now exceeding pre-pandemic highs.

Mercury Marine’s investment in its new, naturally aspirated V-configuration Verado platform, meant to eventually replace the supercharged L6 Verado range, has really paid off. Mercury’s small bore, large displacement V6, V8 and more recently V12, high horsepower offerings have won the hearts and wallets of boaters the world over. The very latest in this line of engines, the just released V10 Verado, looks like another winner. The newly commissioned line dedicated to this newest Verado was in full scale production during our visit, with further capacity scheduled to come on stream as newly installed plant is progressively commissioned.

We saw plenty to be impressed by at Mercury Marine HQ, from the latest largely automated aluminium and steel casting technology to some more traditional, but soon to be phased out, hand-casting techniques used for part of Mercury’s stainless-steel propeller production.


Then there’s their fully automated component machining and leading-edge assembly methodology, which in the most modern parts of the facility dispenses altogether with the overhead trackways of traditional production lines. Even the ‘dirty’ areas – casting, corrosion protection coating and paint – are clean and free of fumes. It’s a thoroughly modern facility.

Along with rigorous quality control on the factory floor, Mercury Marine regularly plucks components off the line for testing as part of its verification process. This happens at every stage of the production cycle, with specialised testing facilities scattered throughout the plant.

Another extremely interesting tour was Mercury Marine’s Noise, Vibration and Harshness (NVH) testing facility located in its own building over the road from the main plant. This is a new addition to the Fond du Lac complex which allows the company to test and refine its engines. Mercury claims its newest engines are the quietest, most refined outboards ever built – and it’s in this testing facility that those claims can be empirically proven or otherwise. Data from this testing is used to further improve Mercury’s products.

Although cameras were not allowed inside this high-tech testing facility, which uses powerful computers running bespoke software to analyse data from a battery of highly sophisticated acoustic, optical and vibration sensors, it left an indelible impression in my mind.

The NVH test pod is a circular, domed sound studio walled with geodesic acoustic baffles. Its sound-insulated floor is physically isolated from the rest of the building, there’s a door large enough to admit the largest outboard, and a test bed slot in the middle of the floor with a water chamber beneath it for engine testing.

Walking into the room is like entering a cone of silence – there is no sound from outside and even sounds inside, like footfalls, sound flat. There is no echo whatsoever, but you can hear the slightest whisper from across the room. The chamber is as close to acoustically perfect as it’s possible to get, which allows the technicians to collect, analyse and compare high-quality noise, vibration and harshness data for every Mercury engine – and the engines of its competitors.

There was more to see, like state-of-the-art lost foam casting for engine blocks and powerheads, which was almost completely automated, as was machining crankshafts, prop shafts and other components. Interestingly, unlike the legacy lines, this latest milling, turning and cutting technology doesn’t require the usual cooling and lubricating fluid during machining.


Mercury Marine’s headquarters at Fond du Lac manufactures more marine engines than any other factory in the world. Mercury designs and builds engines specifically for marine use (rather than adapting automotive designs) and it’s clear from Brunswick’s ongoing investment in expanded manufacturing capacity and capability that it has confidence global demand for Mercury Marine products will continue to grow.

The Fond du Lac facility is impressive on so many levels: logistics, technology, innovation and scale. It’s easy to see why Mercury Marine leads the way in marine engines.