• Simon Motorsports Mercury V6 Alternator System

    High performance outboard-powered boats are not just the toys of racers anymore. For the past twenty years, racing outboards have become increasingly popular in the consumer market, and the presence of these high-performance powerplants is a common sight at boat launch ramps these days.

    These outboards appeal to many performance boaters for many reasons – the main one being increased power without the extra weight. For example, a 200 horsepower Mercury 2.5 liter engine weighs roughly the same as its 280 horsepower counterpart, yet produces almost a third less power. With performance lake boats, bass boats, and offshore boats safely pushing higher speeds, today’s performance boater wants all the horsepower he/she can get.

    What is the drawback of these high-powered race machines? Unlike consumer-oriented outboard engines, high-performance outboards generally have very low-amperage charging systems. Actually, they really don’t charge the battery much, if at all. The average 16-amp charging system in a 2.5 Liter, 260 horsepower Mercury high-performance outboard is sufficient to operate the fuel pump, engine systems, and trim systems, however, there’s really little overhead left for charging the battery. This is by design, since these outboards are designed for one purpose – maximum power output. Larger charging systems increase parasitic horsepower loss, since greater energy is required to pass stronger magnets over the stator windings.

    The average V6 consumer outboard engine is equipped with a charging system that is capable of 40-60 amperes of output – quite a difference from their race-equipped counterparts. A 40-amp charging system could easily handle electrical accessories such as depth finders, large-screen GPS systems, and of course, custom stereo systems. There is another concern for fuel injected engines. The EFI systems require high and low pressure fuel pumps, which draw a lot of current. Sometimes, the addition of electronic accessories leaves insufficient electrical current left over for the fuel pumps, and the potential for running the engine lean is a possibility. The results of this situation could be serious engine damage, requiring a major rebuild, or even worse - replacing the engine powerhead.

    Modern Mercury high performance outboards such as the 280 horsepower, 2.5 Liter EFI engines have factory-mounted alternator systems, which provide more power (60 amps) than the conventional systems in previous Mercury V6 outboards, however, owners of everything below and older than the 280 horsepower engines do not have this option. With so many high performance 2.4 and 2.5-liter Mercury engines in recreational use today, a solution to this charging system deficiency became a common cry for users of these engines.

    Simon Motorsports, located in Alpine, California has an answer to those that own consumer and high-performance Mercury 2.0, 2.4, and 2.5-liter engines and desire greater charging power. It is a custom made, outboard mounted 50-amp alternator system that is belt driven from the engine flywheel. Best of all, it installs in 15 minutes. Interested? Read on…


    This kit is designed to work in conjunction with your engine's factory charging system. This has two benefits. First, it allows for a total of over 65 amps of total charging power (more on consumer-market outboards), which is greater than any performance outboard engine on the market. Second, it simplifies installation, since the existing charging system does not have to be modified or removed. The important thing to note here is that this system adds 50 amps of charging power to your existing charging system, regardless of factory current output.

    Our evaluation unit is a final production piece, and as such, its quality will be representative of the current offering. My first impression of the system upon inspection was that it was a precision-machined product of extraordinary quality. The aluminum brackets are fully polished, and the machined surfaces are precise and finished perfectly. Our hardware was polished, but the system brackets are also available in powder coated finishes. The alternator itself is a high-quality 50-amp unit, completely clad in chrome, and tested for extended use beyond 8500 rpm.

    The system includes everything you’ll need for the complete installation onto any 2.0, 2.4, and 2.5-liter Mercury engine. It must be noted however, that when installed, the alternator system does add several inches of width to the engine, therefore, only an “Alien” style Mercury cowling (factory or aftermarket) can be used once this system is installed. Due to the alternator's high output, the engine must be equipped with a voltage regulator to avoid an overcharging condition. Fuel injected engines already have this component, but many carbureted models do not, so it must be added.

    The complete kit consists of both alternator brackets, the alternator itself, the drive pulley, extended flywheel pulley bolts, extended head bolts, a drive belt, a pre-cut and crimped positive lead to the engine starter solenoid, spacer washers, and thread-locking compound.

    The total installation time (not including cowl swap) should take no longer than 15 minutes, using common hand tools. The tools required for the job are a torque wrench, flywheel holding tool, and various SAE nut sockets and hex drivers.


    • The first step is to disconnect the negative terminal from the battery. If you own a fuel-injected engine, disconnect the ECM harness, since you will be rotating the flywheel during installation. If you own a carbureted engine, remove the spark plug wires to prevent accidentally starting the engine.



    • Using a suitable flywheel holding tool, secure the flywheel while using a socket wrench to break loose the eight flywheel hub bolts. Remove the flywheel hub bolts and carefully remove the spreader ring plate underneath. This procedure applies to all flywheel types. For this installation, we used a JSRE Drag flywheel.



    • It is important that all mating surfaces on the flywheel, pulley, and spreader ring plate are completely free of dirt or paint. These contaminants will affect the alignment of the flywheel pulley. After insuring that all surfaces are clean, carefully place the flywheel on top of the hub, then place the flywheel pulley on top of the flywheel (see picture to note position of the pulley). Place the spreader ring plate over the pulley and align the flywheel parts. Locate the eight 5/16-inch grade-8 extended flywheel pulley bolts from the Simon Motorsports alternator system. Apply a modest amount of thread locking compound to the last five threads of the bolt and thread it in – finger tight only. Repeat this step for the remaining seven flywheel bolts, and snug the bolts with a socket wrench, being careful not to cut your hands on the flywheel starter teeth. It might be wise to wear work gloves for protection while handling the flywheel.



    • Secure the flywheel with a flywheel holding tool, and begin torqueing the flywheel hub bolts to 30 ft. lb. Be sure to torque the bolts in a cross pattern, four bolts at a time. For example: 9, 3, 12, and 6 o’clock, then repeat on the remaining four.



    • Next, remove the upper starter mounting bracket and set it aside. Locate the Simon Motorsports upper starter alternator bracket and position it with the alternator mount facing upward (see picture). This replaces the Mercury upper starter bracket. Don’t forget to replace the negative battery terminal if so equipped at this location. Apply a small amount of thread locking compound to the threads of the two 5/16-inch hex key bolts and torque them to 20 ft. lb.



    • Remove the two upper right bolts from the starboard cylinder head and set them aside. Position the rear alternator bracket over the cylinder head as shown. Slide one 3/8-inch washer over each of the two Simon Motorsports grade-8 3/8-inch cylinder head bolts, and secure the rear alternator bracket with these. Torque to 40 ft. lb. Note: The kit includes four 3/8-inch spacer washers that are positioned on the inside of the cylinder head bracket, if needed. These may be useful for installations that require more belt tension due to milled heads. Install the bracket without the washers, and if more belt tension is needed, add as necessary.



    • Locate the red positive alternator wire and secure it to the alternator’s mounting stud. Locate both Simon Motorsports 3/8-inch hex head alternator mounting bolts and stainless washers. Secure the alternator to the brackets as shown, using a small amount of thread locking compound on the bolts. Torque to 20 ft. lb. Be sure that the alternator is not pinching any wires in the vicinity.



    • Locate the alternator drive belt, and place one side around the alternator pulley. Place the other side of the belt halfway around the cylinder head side of the flywheel pulley (see picture). While holding the belt in position against the flywheel pulley, use a socket wrench to rotate the flywheel clockwise, and slowly load the belt on the pulley. Be careful not to pinch your fingers on the belt as it engages the pulleys. Continue rotating the flywheel until the belt is completely loaded onto the flywheel pulley. Check the belt tension - there should be no more than ½-inch of deflection in the belt. If more belt tension is required, remove the alternator and the rear bracket, and add one set of spacer washers.



    • Connect the alternator positive terminal to the positive stud on the starter solenoid. Check to make sure no wires are near the flywheel teeth, and that all electrical connections are secure. Reconnect your ECM or spark plug wires and your battery. After five hours of operation, check your belt tension and re-torque your cylinder head bolts.



    • For this system to be effective, the parts must be machined to extremely close tolerances. Simon Motorsports does not disappoint here - the aluminum engine brackets fit perfectly, as does the alternator assembly to those brackets. Installation could not have been easier and more pain-free. Total installation time of the system itself was about 15 minutes.



    • With the system installed, I started the engine and ran it through varying speeds. The driven belt makes no noise, and there is no perceived flexing or stressing of any components. This was important, since the system does not rely on a belt tensioner, rather, it is engineered to work perfectly with its provided belt (which, by the way, is a standard V-belt).


    The first thing that became apparent was that my engine did indeed idle smoother than it had previously. With a fully stoked fuel pump, the engine seems very happy at idle speeds and beyond. A view at the volts gauge quickly confirmed the added juice in the charging system (see video). The power trim system also appreciated the extra boost, and the added amps kept the power trim motor operating at full speed. While running the fuel pump and the power trim, indicated system volts did not drop below 12.

    It should be noted that for the purposes of this test, we removed the voltage regulator on our engine. This was done to illustrate the charging power of the alternator system relative to that of the stock unit. This was for the test video only, and the engine should not be used without a voltage regulator present, or you run the risk of overcharging your battery. As mentioned, fuel injected engines are factory-equipped with a voltage regulator, however, many carbureted models are not. In this case, one would have to be added.

    Finally, In addition to the above mentioned virtues, this product adds a great deal of visual appeal to the engine. I mean, who wouldn't like polished aluminum and chrome on a high performance engine? This is one trick piece that looks as good as it works.

    The complete system is available direct from Simon Motorsports for $695.00 for polished brackets, and $745.00 for optional powder coated brackets in your choice of red, blue, or purple. It's a an impressive product that is perfectly engineered to answer the call for a hotter charging system for high performance Mercury outboard engines.
    Comments 2 Comments
    1. Mikeyo's Avatar
      Mikeyo -
      I purchased and installed alternator but am wondering how to check voltage to ensure it's charging properly.
    1. CNC_Guy's Avatar
      CNC_Guy -
      Do you still have pics available?