Kohler Marine Generators

A Generator Business Founded Before Almost Any Yacht It Now Powers

Kohler Co. itself dates to 1873, a Wisconsin foundry making agricultural implements before it ever made a generator or a bathroom fixture. The generator business is younger but still runs past its own centenary: in 1920 the company built what it describes as the world's first engine-powered electric generator, a four-cylinder gasoline unit producing 1,500 watts of 110-volt DC power under the name 'Automatic Power and Light.' It was built for farms without utility electricity, but its portability got it noticed well outside agriculture. Kohler's current marine product literature still carries the tagline 'In Power. Since 1920,' and that date is not marketing rounding: it is the same year the first unit shipped.

The best-documented early adopter was Admiral Richard Byrd, who took five Kohler generators on his first Antarctic expedition in 1926 and seven more on his return in 1933. According to company-history accounts of the expeditions, Byrd's team found the 1926 generators still in working order when they revisited the original base station seven years later, in conditions about as hard on an engine as exist anywhere on the planet. Kohler moved into mass production of its own small engines by 1948, and the marine diesel line sold today is a direct descendant of that same engineering culture: sealed, sound-shielded gensets built to run unattended in a wet, vibrating, hard-to-access engine room, which is a different design problem than the standby genset sitting quietly in a suburban side yard.

What Changed in September 2024: Kohler Is Now Rehlko

The transaction closed in May 2024 and the new name was announced that September, pronounced 'REL-co' and derived from the letters of Kohler itself. Rehlko now owns and runs the marine generator business, the parts network and the warranty programme; Kohler Co. holds a minority stake but no longer controls day-to-day operations of the division. In practice this means the physical generator on a boat still reads KOHLER on the housing, badge and control panel exactly as it always did, because Rehlko has been transitioning the brand gradually rather than swapping every casting overnight, but the entity standing behind the warranty, the parts supply chain and the dealer network is now Rehlko, not Kohler Co.

For an owner this matters in one practical way: a warranty claim, a parts order or a service contract signed before the rebrand references a company that, strictly speaking, no longer runs the business, even though the product line, the model numbers and the authorised dealer network have carried over largely unchanged. A used-boat buyer inheriting a five- or ten-year-old Kohler set should confirm with the selling dealer or Rehlko's own marine parts desk that support for that specific model has continued under the new ownership, rather than assuming Kohler Co.'s reputation and financial backing still stands directly behind it. Nothing found in dealer or trade-press coverage suggests support has actually lapsed, but the corporate reality changed and a buyer should know that before relying on brand history alone.

The nameplate says Kohler. Since September 2024 the company behind it is called Rehlko, and Kohler Co. is only a minority partner in it.

The Range, From a 6 kW Box to a 200 kW Superyacht Set

Kohler's own product guide lists diesel sets in roughly a dozen frame sizes: 5EFKOD/6EKOD, 9EFKOZD/11EKOZD, 13.5 to 24EKOZD, 28 to 40EKOZD, 45 to 65EOZDJ, 80EOZDJ, 99EOZDJ, 125EOZDJ, 150EOZDJ and the 200EOZDJ flagship, each available across multiple voltage and phase configurations for different national electrical standards. Sets from 5 to 11 kW use an Advanced Digital Control IId panel; everything from 12 kW up to the 200 kW flagship uses the more capable Decision-Maker controller. Independent dealers confirm the range holds up in the field: Brags and Hayes Generators, a Florida-based marine generator dealer unconnected to Kohler, sells and lists a 150 kW three-phase unit built around a John Deere 6068AFM85 six-cylinder block, burning a rated 46.1 litres per hour at full load, which matches Kohler's own published range and confirms these are real, sold, installed units rather than catalogue-only figures.

The feature that matters most on anything above about 40 kW is PGEN, Kohler's factory-installed paralleling system, which links up to eight generators of mixed sizes on a single communication wire and lets them share a load automatically. According to Rehlko's own technical material, PGEN was the first factory-fitted, pretested paralleling controller in the marine generator market, meaning a yacht with two or three gensets does not need a separate, custom-engineered switchboard to run them together. Every current diesel set is EPA Marine Tier III certified and carries type approval from Lloyd's Register, DNV, ABS and Bureau Veritas, which is the paperwork a yacht built or flagged to class society rules actually needs, and is a meaningfully different proposition from a residential or industrial Kohler generator wearing the same badge.

Why Kohler Only Sells Diesel Marine Generators Now

The case, WBIP, LLC v. Kohler Co., centred on a patented exhaust system that reduced carbon monoxide in gasoline marine generator exhaust, a genuine safety advance because CO poisoning from generator exhaust had killed boaters. According to the Federal Circuit's own 2016 opinion, Westerbeke demonstrated its 'Safe-CO' low-CO technology to Kohler representatives at a boat show in 2004, and Kohler launched a competing low-CO gasoline gen-set of its own about a year later. A jury found in 2013 that Kohler had infringed, that the infringement was willful, and awarded WBIP just over 9.6 million dollars in damages; Kohler's appeals on validity and on the willfulness finding were rejected by the Federal Circuit in July 2016, and the case was settled on confidential terms that December, as reported at the time by the trade title Boating Industry.

Kohler has not returned to the gasoline marine generator segment since, and its current marine catalogue is diesel-only. That is a real, if second-order, consequence for anyone shopping this brand: a boat owner who specifically wants a gasoline genset, common on smaller outboard-powered boats and some older houseboats, has to look to Westerbeke, Onan or another maker, because Kohler simply is not a competitor in that category any more. For anything the size of a flybridge motor yacht or larger, where diesel is already the fuel aboard, this is a non-issue; it only matters to a buyer who assumed Kohler's product range still mirrors what it sold before 2017.

What a Kohler Marine Generator Actually Costs, to Buy and to Run

Public pricing on Kohler marine generators is the exception, not the rule. Bosch Marine LLC publishes a complete list running from 9,949 dollars for the entry 6EKOD (6 kW) up to 19,680 dollars for the 24EKOZD (24 kW); Central States Diesel Generators separately quotes the same 6 kW class at roughly 10,088 dollars without a sound shield and 12,837 dollars with one, a close enough match to treat the entry-level price as real rather than a one-off list error. Above that size, dealers who otherwise sell the same product line, including Citimarine Store and Yachtaid Marine, do not publish a number at all and route every enquiry through a quote request, and the 99 kW-and-up sets a superyacht would actually specify are not priced publicly anywhere found in this research. That gap is itself the useful fact: a buyer should expect to negotiate a quote for anything above about 25 kW rather than find a reference price to negotiate against.

Installation is a separate, often comparable-sized cost. One owner on Trawler Forum, replacing a failed generator on a Mainship 400 trawler, reported that a same-class Northern Lights 6 kW unit cost roughly 13,000 dollars installed, including a sound shield and controls, a figure that lines up with generic marine-repower cost surveys putting a full generator swap, parts and labour together, in the 10,000 to 14,000 dollar range on a 30-to-40-foot boat. On a new-build superyacht the generator is specified and fitted at the yard as part of the electrical plant design, so the installation cost is folded into the build contract rather than quoted separately; on a retrofit or repower of an existing yacht, expect labour, wiring, exhaust and mounting work to cost at least as much as the generator itself, and get that number in writing before assuming the unit price is the whole bill.

Reliability in Practice: What Owners, Mechanics and Forums Actually Report

Cross-posted discussion on Trawler Forum, comparing Northern Lights against Kohler directly, describes Northern Lights as the more consistently chosen brand in the US market and 'the workhorse of the industry: simple, solid, dependable,' while describing Kohler in the 8 to 12 kW class as capable of long service life 'if set up correctly and maintained properly,' with one boatyard mechanic reporting fewer problems with Kohler units than some competitors specifically because of Kohler's parts overlap with the RV generator market. The same discussion notes that the diesel engine block inside many mid-range Kohler marine sets is a Yanmar 3TN-series unit, not a Kohler-designed engine, which is a common and generally well-regarded industrial base rather than a weakness, but is worth knowing before assuming 'Kohler' names the whole machine.

The complaints that do surface are specific rather than vague: owners on Trawler Forum describe difficulty finding technicians comfortable with the computer-controlled Decision-Maker models, which throw diagnostic codes a general boatyard mechanic may not recognise, and one owner's own decibel-meter reading of an 8 kW set found 72 dB with the sound shield fitted against 85 dB without it, in a cabin where ambient noise ran under 50 dB and the salon fans on high measured 60 dB, a useful real number against a spec sheet that rarely states an in-cabin figure at all. The most consistent thread across the forum discussion, regardless of brand, is that irregular use rather than any inherent design flaw is what actually kills a marine generator: a set run for fifteen minutes a month develops problems no design change fixes.

Who it is for: An owner or buyer specifying or replacing a genset on anything from a 60-foot flybridge to a 40-metre-plus yacht with a Kohler diesel set already aboard, and anyone comparing Kohler against Onan, Northern Lights or Westerbeke before a repower.