Innovation, Engineered for a Zero Carbon Emissions Marine Future

Green House Gas Emissions and Boats:

The Inconvenient Truth

Countless millions of existing commercial and recreational boats pump 40 times more carbon emissions and other pollutants into the water and air we breathe per mile traveled than cars and trucks. Millions of tons of carbon from raw, untreated diesel and gasoline boat exhaust are emitted yearly.

( top left to right) A powerboat, high speed ferry boat ; (bottom left to right) tour boats and commercial craft

All planing boats worldwide use the same non-patented underwater designs perfected in the late 1950's that require excessive amounts of horsepower/energy to reach speeds over 15mph/24 kmh and use marine engines that emit raw untreated diesel and gasoline exhaust into the atmosphere.

Approximately, 90% of all the boats worldwide use this type of “wet exhaust” system shown in the diagram (LEFT), including engines that turn electric generators. The cooling seawater is  pumped through the engine and mixed with the engine exhaust and pumped back into the air and water without exhaust treatment



Many commercial fishing vessels, tour boats, ferries and ships use a “dry exhaust” system. Simply put, the engine cooling radiator is built right into the hull and exposed to cool seawater. “Keel cooling” does preclude mixing the seawater with exhaust gas. However the untreated raw engine exhaust gas is simply piped up through an exhaust stack into the atmosphere.

In April 2018 the International Maritime Organization adopted an “Initial Strategy” on the reduction of GHG emissions calling for strengthening measures, such as: operational efficiency measures, further speed reductions, measures to address CH4 and VOC emissions, alternative low-carbon and zero carbon fuels, as well as market-based measures.


There is a growing need for a low carbon world and the marine industry is faced with regulatory and consumer demand for solutions with lower environmental impact.   For the past 20 years, STec has been at the forefront of developing the latest technologies to lower carbon emissions from offending power boats, while still maintaining speed, safety and overall owner satisfaction.

STec: Evolution and Innovation

The SRD Monohull  2005

The patented SRD 38 (Schulz Reverse Deadrise) was launched 2005 and represented a major breakthrough for innovative power boat design. The SRD hull was developed by Walter Schulz based on a totally new hull design concept proven to reduce horsepower/energy demand by 50% obtaining the same speed/weight ratios as a boat of comparable size. The goal at that time was to significantly reduce fuel burn and the cost of operation. The mid-to- aft hull sections of the SRD 38 are radically different from the sections of all other power boat hulls.  The SRD was the first hull design to be patented since the Starling Burgess planing hull patent in 1937 and later improved for fiberglass by C. Raymond Hunt in the 1950’s.

SRD 38 Seatrials

Cost and Concerns 2005-2008


While the SRD hull concept and demo boat certainly proved to reduce fuel burn by 35%-40% the cost of building new hull molds to incorporate SRD underwater technology for each model manufacturers were building was very expensive. Added to the builder’s cost was the issue that there was little-to-no consumer pressure or demand in the US for reduced fuel burn. Obtaining only 1 mile to a gallon (compared to 23 MPH for autos) was the accepted standard for the powerboat industry and every boat builder was offering the same basic fuel burn performance.

The Mold Cost Solution 2008-2013


To solve the mold cost issue, Walt Schulz purchased a hull mold in 2008 for a 1985 Tollycraft 45’ production power boat. Tollycraft had been out of business for many years and the mold had to be shipped from Seattle. With the Tollycraft hull mold in Rhode Island, Schulz engineered the adaptation of the mold to an SRD underwater configuration that would be cost effective for production boat companies. After a major effort, an economical mold “SRD Insert” concept was developed that was relatively simple to install, economical, and suited to all existing power boat molds in the industry. The SRD Insert is specifically designed for any size boat mold and is non-destructive to the original mold.


The conventional Tollycraft hull ready for mold conversion

The new SRD shape aft after the mold conversion

The Defiance 46' motor yacht with the SRD bottom conversion

Defiance 46' motor yacht interiors

SRD Insert Testing 2014-2016


In 2013, a totally custom 45’/46’ Shannon Defiance was designed by Walt Schulz using the old Tollycraft hull mold with an SRD Insert and a totally new deck design. The Defiance 46 was launched in the spring of 2014 and heavily sea trialed over 2000 miles in every possible sea state and storm conditions. The 46’ was fully outfitted with a finished interior and every conceivable option package. The boat was powered by a single 600hp Cummings diesel engine mounted on the centerline with a 200hp diesel auxiliary engine operating hydraulically-driven twin outdrives which were used only for slow-speed inland waterway use and docking. The Defiance proved to have the same speed performance as any similar-sized and equipped power boat on the market using less than 50% of the horsepower demand.  Additionally, the Defiance showed exceptional smooth non-pounding ride in extreme wave conditions.


SRD and Greenhouse Gas Emissions


While the SRD design and mold insert definitively reduced horsepower demand by 50% and also cut boat diesel carbon emissions by a significant number, however, the emission test results were a disappointment to Walt Schulz. He came to the realization that marine diesel engine carbon emissions, even with the new, efficient, common rail diesel engines, were still horrendous compared to cars and trucks on the road. The fact that there are currently no emissions standards for marine craft or inspection requirements has created a terrible environmental situation. All boats, including the Defiance 46, have no catalytic diesel exhaust treatment, a critical factor in reducing carbon emissions. Available equipment like SCR (Selective Catalytic Reduction) for diesel engines designed for truck engines is difficult and expensive to adapt to marine engines due to the high temperatures and required air space. It was obvious that the SRD concept needed a totally new method of propulsion for 21st century climate change crisis demands.


SRD 2014-Present


After years of R&D it was finally determined that even marine diesel hybrid electric propulsion was not going to meet new stringent emissions regulations. Compounding the problem, automotive type hybrid electric technology was not easily adaptable to boats due to engine, lithium batteries and electric drive motor critical cooling demands and other issues. Since 2014, Schulz has dedicated his time and focus to overcome challenges in the development of new clean energy propulsion systems. Today STec has resolved all the marine hybrid electric problems with IP patentable solutions and that, in addition, are engineered to accommodate future advances in battery technology for 100% electric propulsion and other advances like hydrogen fuel cell energy.


The SRD Hull Conversion: Clean Energy for All


SRD offers an economical solution to reduce carbon emissions for all future boats worldwide. The SRD concept encompasses hybrid electric, liquid cooled, automotive based CNG or gasoline propulsion with patented SRD insert conversion to existing boat hull molds. This technology allows boat manufacturers worldwide to use their existing above-water and interior designs, deck and interior molds and tooling, achieving the same 50% reduction in engine horsepower and 90% carbon emissions reduction while maintaining the same look and style of their current boats.



Working toward a net ZERO carbon footprint

STec, Inc.
Bristol, Rhode Island
New Bedford, Massachusetts