Figure 1. The usual starboard cylinder bank arrangement of inlet and exhaust ports in a two-stroke-power-cycle V-block engine is shown in this sketch.
The E-TEC G2 (for second generation or generation two) engines were developed as further enhancements of the legacy E-TEC (which afterwards began to be denoted as the E-TEC G1 engine, although this designator was never used by Evinrude). The E-TEC G2 engine was developed in three distinct engine block configurations, and each engine series was revealed at separate times.
The first E-TEC G2 engines were revealed in June, 2014, at a dealer-only event held in Wisconsin. This initial group of E-TEC G2 engines used a 74-degree V6 block with 3.4-liter displacement, with the same bore (3.854) and stroke (3.000) dimensions of the legacy E-TEC engine, and ranged in power from 200 to 300-HP. None of this was considered unusual. The innovation in the engine block design was the entirely new design for the combustion chambers and their non-mirrored layout. Previously, most V-block outboard engines used a mirrored design, that is, the starboard cylinder bank was mirrored in the port cylinder bank, with the exhaust ports on both banks toward the center. The E-TEC G2 abandoned this approach, and instead it used a starboard-starboard cylinder bank design.
To understand the concept behind the starboard-starboard design for the two cylinder banks, the conventional V6 two-stroke-power-cycle design using mirrored banks must first be understood. In the conventional design, the location of the inlet and exhaust ports on the cylinders changed sides on the mirrored port bank. Figures 1 and 2 illustrate this concept.
Figure 1. The usual starboard cylinder bank arrangement of inlet and exhaust ports in a two-stroke-power-cycle V-block engine is shown in this sketch.
During the downward power stroke the cylinder wall on the right (as seen in Figure 1) is receiving a force pushing the piston against it due to the offset of the connecting rod from vertical at the attachment to the crankshaft. The right side cylinder wall is generally cooler because the cool fuel air charge flows into the cylinder on that side.
Figure 2. The usual port cylinder bank arrangement of inlet and exhaust ports in a two-stroke-power-cycle V-block engine is a mirror of the other bank. Note how the exhaust port is now on the right side of the cylinder, the opposite of the arrangement on the starboard bank.
During the downward power stroke of the port bank pistons, the cylinder wall on the right (as seen in Figure 2) is still receiving a force pushing the piston against it due to the offset of the connecting rod from vertical at the attachment to the crankshaft. The right side cylinder wall on the port bank is generally hotter because the hot exhaust gases flow out of the cylinder on that side. The greater heat means more wear on the piston rings and cylinder walls from the sideways force on the piston.
In conventional V6 outboard engines using mirrored cylinder banks, a compensation was made for the unequal side forces on the pistons: the piston shape was not made perfectly circular. Special cam-ground slightly non-circular pistons were manufactured. This method can be deduced when an engine specifies a specific piston part number use in a specific V6 engine bank cylinder.
The design of a non-mirrored V-block engine using the a starboard bank arrangement of inlet and exhaust ports for both port and starboard banks eliminated the problem of the port bank cylinder's right wall being the hot exhaust wall. This approach was intended to eliminate a tendency for the port bank cylinders to be more prone to damage due to the hotter temperature on the cylinder wall receiving the sideway force on the piston.
A further advantage claimed by Evinrude for the starboard-starboard design of the engine block was the elimination of the exhaust passage on each bank joining into a common exhaust passage near the cylinders. Keeping the exhaust passages separate from each other for the two banks was suggested to be a further enhancement in the ability to produce power output and to reduce restriction of exhaust gas flow out of the cylnders.
In addition to the unusual starboard-starboard V-bank design, the E-TEC G2 engine combustion chamber also received extensive research on how the air-fuel mixture and the exhaust would circulate inside the cylinder during actual operation and combustion. To accomplish this analysis, Evinrude engineers employed advanced computer modeling and very powerful computing power.
In association with the University of Wisconsin at Madison, Evinrude engineers used a software package based on KIVA to predict the complex interactions that would take place in the combustion chamber. The KIVA software was developed for thermo-dynamic simulations originally done at the Los Alamos National Laboratory for research into weapon design. The transference of this technology to engine combustion chamber design occurred when automobile manufacturer were trying to improve fuel economy and lower emissions in their vehicles to comply with EPA emission limits and CAFE fuel economy mandates.
By using advanced computer modeling of the combustion chamber, thousands of variations in cylinder and piston design could be evaluated by simulation instead of creating prototype engines for actual testing. This use of sophisticated combustion chamber simulation software was apparently the first time it had been employed by Evinrude for the design of its outboard engines. Whether any other outboard engine manufacturer had or have used similar simulation software to refine their engine designs is unknown. Evinrude was apparently sufficiently proud of this work and the patent obtained, that they used it in promotional presentations to dealers.
A sample of the modeling software output can be seen in a short presentation from UW-Madison.
To effectively use the KIVA software for the complex engine modeling, extraordinarily powerful computer hardware was necessary. Evinrude used X-ISS high-performance computing (HPC) clusters to get the necessary computation power, and eventually expanded their system to include more "compute nodes" to facilitate faster performance.
The ultimate design of the combustion chamber that was developed for the E-TEC G2 was determined to be a new and useful invention, and the design protected by a patent. The descriptor "PurePower Combustion" was applied to the E-TEC G2, representing the improvements obtained: more complete combustion of the fuel, producing more power output per volume of fuel, and thus producing less exhaust gas contaminants for a more pure exhaust. The cumulative effects were a win-win-win situation: less emissions, better fuel economy, more power output
At some point in the design of the G2, Evinrude planned for the 300-HP engine to have a special model that would use an unusual arrangement of the exhaust port to improve power output at high engine speeds. The technique was known as RAVE, which stands for ROTAX Adjustable Variable Exhaust. (ROTAX is another engine manufacturer also owned by BRP, the corporate parent of Evinrude.) On RAVE two-stroke-power-cycle engines, there is a mechanical method employed to change the size of the exhaust port opening, with the purpose of increasing the size of the port opening under certain conditions. The RAVE method had already been used on small E-TEC engines, usually two cylinder engines, used on the SkiDoo snow machines. The RAVE system was typically actuated when very high throttle settings were used to accelerate the engine speed. Some media in attendance at the G2 introduction reported they had test-driven a 300-HP RAVE model boat made available by Evinrude.
The intention to use the RAVE method can be deduced by the cowling design of the initial G2 engines; there was a raised area on the side of the cowling that was apparently intended to accommodate the RAVE hardware. This was generally known as "the RAVE bump." But when the final design for the production of G2 was ready, the RAVE method was not used. The inference: the G2 large V6 could reach the needed power output without the added complexity of the RAVE system. The cowling molds with the bump were not immediately replaced.
For the highest power output models, the 300-HP and the 250 H.O. (High Output) engines, Evinrude also may have employed another power-enhancement technique: a water spray directed into the engine exhaust passageway to alter the exhaust gas mixture density, which in turn would change the resonance of the exhaust passage. By this technique the exhaust chamber could be "tuned" to produce a boost in the flow of air through the combustion chamber. The more air in the combustion chamber, the more fuel that could be burned, and the power produced. This technique is not often mentioned in reviewer comments, and its existence was actually a surprise to me.
The E-TEC G2 was a completely new, clean-sheet design, and there were literally almost no components in common with the legacy E-TEC, other than a few shared parts: a fuel filter, some sensors, and some bearings.
Among the many innovations, two new features stand out: these G2 engine were all controlled by electronic shift and throttle mechanisms; the usual mechanically linked remote controls were gone. Also, these G2 engines provided their own internal hydraulic steering actuator mechanism (and as an option) with an internal hydraulic boost pump.
These innovations had some side effects. The G2 would not be popular as a replacement engine on an existing boat due to the need for new controls and possibly new steering. The weight of the G2 had also grown, with a 25-inch shaft model with power steering now weighing 568-lbs, an increase of 44-lbs from the 524-lbs of the legacy E-TEC 3.3-liter engines. Some of the gained weight would be offset by removal of an external steering actuator, which would likely weigh 15-lbs.
The integral steering mechanism was not without problems in actual production engines. Because the steering system was completely integrated into the engine mount, working on the steering system in the field by dealers was very difficult. In many instances the entire powerhead, midsection, and gear case have to be removed from the engine mount in order to have access for repairs. Also, field repairs were deemed unlikely to be effective, so Evinrude had to employ warranty-replacement steering systems to cure problems. This approach was, of course, a considerable (and unanticipated) warranty expense for the G2, as well as a considerable annoyance to customers, whose engines were often out of service at a dealer awaiting the replacement of the steering.
Evinrude had already offered the option of an electronic shift and throttle (EST) remote control system called ICON for their legacy (or G1) E-TEC engines. For the G2 engines the use of EST controls would no longer be an option—it was now standard. The system was designated ICON II. A significant improvement over ICON EST was the use of two data communication networks connecting the engine to the remote controls; the earlier ICON EST system used only a single network. With ICON II controls, the two networks were designated as Private and Public. The Private network was the primary control network for communication between engine and remote controls. The engine and controls were also connected to a Public network—the usual boat NMEA-2000 network. In the event of a communication failure on the Private network, the controls would automatically shift to using the Public network.
For customers that insisted on using conventional mechanical remote throttle and shift controls, Evinrude designed an interface box. The mechanical controls could connect to the interface box, and their movements converted to digital signals sent to the engine on the Private network. This was the solution to backwards compatibility.
The styling of the engine, the colors available, and the general overall appearance were a very significant departure from any previous outboard engine, and many boaters expressed their objections to the visual appearance of the G2. In one Evinrude public presentation, it was remarked that the very distinctive appearance was intentional, in order that "an Evinrude engine could be recognized at 100-yards at dusk."
The second series of E-TEC G2 engines was introduced two years later, in June 2016. These engines used a 66-degree V6 block of 2.7-liter displacement, and were available in models of 150 to 200-HP. Curiously, the starboard-starboard block arrangement used on the earlier G2 engines was not employed on these models. Because these engines produced significantly less power at their highest rating, the normal mirrored bank design was probably deemed sufficient for the V6 block at those power levels.
In the legacy E-TEC smaller-displacement V6 engine, a 60-degree V6 block design was used, which was considered a good approach for balance. The 66-degree block with a mirrored-block arrangement allowed for more space between the cylinder heads which could be used for larger and better tuned exhaust passages, while not creating too much unbalance from the more desirable 60-degree configuration.
By assumption, the combustion chamber design must have also been carefully modeled for enhanced performance, as was done in the larger V6 G2 design.
The small-displacement V6 G2 engines were available without the internal hydraulic steering. This configuration was designed the TRAC+ midsection (pronounced "track plus""). The engine weight was viewed as disappointing: a 25-inch shaft without integral steering weighed 507-lbs; with integral power steering, the weight increased to 541-lbs. Compared to the initial 200 to 300-HP G2 engines at 568-lbs, these "smaller" models only weighed 27-lbs less. The use of electronic shift and throttle controls was continued.
The third (and final) series of E-TEC G2 engines was introduced with another three years interval delay in June 2019. These engines used a new three-cylinder in-line block of 1.865-liter displacement, and were available in power ratings of 115 H.O., 140-HP, and 150-HP. The 150-HP model used an unusual exhaust design in which water was sprayed into the exhaust to alter the resonance of the exhaust passage and enhance the engine power at peak engine speeds. (Evinrude had used this technique on some legacy E-TEC models.) Again, electronic shift and throttle controls were standard, which was a significant departure from prior three-cylinder outboard engines. The cowling styling was more muted, and white was the base color. Again, some versions were available without integral steering. The engine weight was attractive for the power range covered. A 25-inch-shaft model without integral steering was 401-lbs.
Looking at the dimensions of these three engine series shows some interesting similarities and differences:
Block Bore Stroke Cu-Inch Liters MaxHP HP/L HP/CYL L/CYL V6 3.854 3.00 210.00 3.441 300 87.4 50.0 0.572 V6 3.39 3.10 167.88 2.751 200 72.7 33.3 0.458 I3 3.854 3.25 113.51 1.860 150 80.6 50.0 0.62
The large-block V6 300-HP and 250 H.O models and I3 150-HP model used a water spray in the exhaust method to boost power output. This method of boosting horsepower was not used in the other E-TEC G2 engine models. The comparison also assumes that the power output produced was the nominal power as indicated in the engine model rating. Because engine power ratings are often rounded to certain even values, the actual power output could differ from the rated power output by perhaps six percent, according to the ICOMIA rating system generally used.
A trend appears in the above data: as the E-TEC G2 engine evolved, the newer 2.7-liter V6 models tended to produce less power per liter of displacement at the highest power model. The initial 3.4-liter V6 with a 300-HP rating produced the most power-per-liter displacement; the follow-on 2.7-liter V6 with a top rating of only 200-HP produced significantly less power-per-liter displacement. The final 1.86-liter I3 models also produced more power per liter than the small-block G2 engines. A second trend is the displacement of one cylinder: there is no consistency. The biggest cylinder displacement is on the I3 engine; the smallest cylinder displacement is on the small V6 engine.
One possible outcome of the variations in cylinder displacement might be that the less displacement per cylinder and lowest power output per displacement might suggest that the G2 small V6 block could have the least stress on the cylinder components like the pistons, rods, rings, and ports. Those considerations could lead to a longer and more trouble-free service life.
The table below shows details for the lowest power output in each block version.
Block Bore Stroke Cu-Inch Liters MinHP HP/L HP/CYL L/CYL V6 3.85 3.00 209.55 3.434 200 58.2 33.3 0.572 V6 3.39 3.10 167.88 2.751 150 54.5 25.0 0.458 I3 3.85 3.25 113.51 1.860 115 61.8 38.3 0.62
The trend now flips: the smallest displacement engine, the I3, makes the most power-per-liter in its lowest-power version. The small V6 engine, again, seems to be the least stressed engine in terms of power-per-liter and power-per-cylinder. If looking for the most conservatively rated engine, the 150-HP V6 model is the choice. It produces the least horsepower-per-cylinder and the least horsepower-per-liter displacement. An E-TEC G2 V6 150-HP engine should be a long-running engine in terms of stress on the combustion chamber, pistons, rods, bearings, and so on.
An additional metric to consider is power-per-pound. For simplicity the comparison will be based on 25-inch-shaft standard-rotation models with non-power integral steering (the IHS designator).
Block Liters HP LBS HP/LBS V6 3.343 300 558 0.53 V6 3.343 200 558 0.35 V6 2.751 200 533 0.375 V6 2.751 150 533 0.28 I3 1.860 140 408 0.34 I3 1.860 408 408 0.28
The best power-to-weight ratio occurs in the 300-HP large V6 engine; The worst power-to-weight ratio occurs in the 150-HP small V6 engine and the 115-HP I3 engine.
The 2022 specification sheets for 11 models of the E-TEC G2 engines are available for download as PDF files from the listing below.
The specification sheets use several brand names and acronyms to describe the steering system options available in these E-TEC G2 engines. The various steering system configurations contribute to changes in the weight of the particular engine models. These brand names and acromyms are explained below.
DISCLAIMER: This information is believed to be accurate but there is no guarantee.
Copyright © 2022 by James W. Hebert. Unauthorized reproduction prohibited!
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This article first appeared May 2022.
Author: James W. Hebert