OptiMax JP

An animation showing the fuel combustion cycle in a direct fuel injected 2-stroke Mercury OptiMax engine.
The OptiMax JP outboard runs on JP5, JP8 and commercial Jet A aviation fuels.

One of my posts in our Virtual Tour series focused on consumer outboards. For the government, we build a “stealth” outboard that is rarely seen:  the OptiMax JP.  Developed for the U.S. Department of Defense, this multi-fuel engine runs on JP5, JP8, kerosene and Commercial Jet A aviation fuels — the same “heavy” fuels used in helicopters and jets (which DoD already stockpiles all over the place). The 3.0 Liter V-6 OptiMax JP produces 185 horsepower. These unique engines are 40% more fuel efficient than the gasoline engine they are derived from.  And, with 95% shared components, there are no unique training requirements necessary. Mercury JPs have been deployed around the world for some time now.  Tony Nahitchevansky is our Government Accounts Manager. I called Tony to get some background information regarding the development of this multiple fuel engine for our armed services.

“A Navy ship crash in 1995 which resulted in a explosive gasoline fire spawned a DoD directive for all gasoline powered engines and gasoline fuel tanks be removed from Naval ships by 2010,” Tony said. The mandate called for engines to be developed to operate on fuels that meet the following criteria:


JP OptiMax engines prepared to ship.

1) Improve ship safety by minimizing fire hazards

2) More economical and more efficient

3) Readily available as a single battle space fuel

Tony said every ship carries JP 5 fuel. Ports have JP8 and Commercial Jet A available. The common denominator with all three fuels is  availability. “An unlimited fuel supply enhances our ability to protect assets on the water,” said Tony.  It also greatly increases crew safety. Tony said, “There was another ship fire since the 2010 DoD mandate. The fact that the ship only had JP aviation fuels on board provided the crew enough time to react and save the ship in a safe and efficient manner,” said Tony.

An OptiMax JP powered Sea Fox USV awaits its next mission.
A Sea Fox unmanned surface vessel (USV) in hot pursuit.

The OptiMax JP has been a resounding success. Hundreds of engines were deployed on Army high speed combat craft during the Iraq war. In another program, the OptiMax JP powerhead was mounted to a Mercury Sport Jet pump, which is the propulsion for Sea Fox USVs (unmanned surface vessels). “Sea Foxes are currently in use in the Iranian theater. These remote controlled vessels are deployed to protect and escort U.S. war ships in International waters,” said Tony. The Army uses OptiMax JPs on their riverine combat craft and the Navy uses them on their 8 meter target boats.

The 8.5 meter composite rib under construction. Photo courtesy Structural Composites.
Twin OptiMax JP outboards rigged on the 8.5 meter Structural Composites rib.

Twin OptiMax JP outboards rigged on the 8.5 meter Structural Composites rib. Photo courtesy Structural Composites.

Structural Composites, Inc., is one private sector company currently running JPs. They have developed a 8.5 meter composite rib for the Navy. I called Structural Composites rep Scott Lewit to get some feedback regarding their hull and OptiMax JP experience. Scott said their rib is unique in the manner in which it is constructed. The use of space-age composite materials resulted in a 40% weight savings to comparable sized hulls.

Scott said, “The Navy is moving toward lighter craft so our composite construction is a perfect fit. That, and the power-to-weight advantage you get with outboards compared to traditional inboards or sterndrives, is huge. Outboards are also easier to swap should you encounter an issue,” said Scott. The DoD’s 2010 mandate for the removal of flammable fuels  from ships along with the Navy’s need for “instant readiness” all point to the OptMax JP. Its a natural fit,” Scott said. Outboards are also much easier to integrate in with Structural Composite’s shock mitigation system which separates the hull from the deck. (That way, hull impact shocks are softened – not transmitted directly to the bodies of highly trained troops.)

The OptiMax JP powered composite rib undergoing sea trials. Photo courtesy Structural Composites.
A close-up view of Structural Composites’ 8.5 meter rib. Photo courtesy Structural Composities.

Scott continued, “The JPs are wicked fast.  Acceleration is 0-50 in ten seconds and tops out at 72 MPH! Equally impressive is the fuel economy. We are seeing four miles-per-gallon (mpg) at 40 mph, and respectable 2 mpg at 60-70 mph. I really like the responsiveness of the engines. That, combined with the lightweight composite hull construction, makes you feel connected to the water. The twin OptiMax JPs provide instant power – and a great sound,” Scott exclaimed.

Structural Composites’ 8.5 meter rib will be on prominent display at the entrance to the 2012 IBEX (International Boat Builders’ Exhibition & Conference), October 2-4, in Louisville, Kentucky. They are also a sponsor of a seminar on composites. If you’re a law abiding civilian and in the marine industry, this may be your only opportunity to see one in person. If you’re a bad guy, better hope you never do.











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6 thoughts on “OptiMax JP”

  1. Hello Rick or Mercury Team.,

    I have one question to ask you.When you start working on the JP outboards., I know you mention it can run on diesel fuel for short time but the question is which type of diesel fuel you ran that time, LSD ( Low Sulfer Diesel ) or ULSD ( Ultra Low Sulfer Diesel)? if LSD, I know it can cause some issue with the exhaust ports, but with ULSD it should be not too bad. It will be much cleaner than LSD is.

    Thanks for reading this question.

    Note: I do still have 1963 Mercury 850 series outboard with me and still running like new ( that engine can burn almost any fuel I run thru but seems the unleaded gas / Kenornse mixure that where I get best fuel mileage).



    I enjoying reading the blogs in here keep up good work.

    1. Hi Marc:

      The ULSD would be best to run. What we discovered was that sulfur deposits build up over time on the dome of the piston as well as in the ring grooves. The ULSD burns cleaner.


      1. Bonjour ( Hello ) Rick.,

        I do agree with your comment regarding of using the ULSD and I did some of the researching of sulfur level between the conventional Jet fuel and ULSD and the interesting twist is that the ULSD have lower sulfer level than conventional Jet fuel.

        I know it may surprised you on this part but ask one of your testing crew to run thru the ULSD for X number of hours and take a bore scope and look at the exhaust port to see how much it build up vs. conventional Jet fuel.

        (I do live in France and the fuels are more expensive than what the USA is at now.)

        Merci (Thanks),

  2. Rick,
    Looks like a really unique and heavy duty unit.
    Looking at buying a govt surplus JP unit for use on my boat. Can I use ULSD as primary fuel all the time or is it recommended to use Jet A or Kerosene?

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