A guide to Mercury Marine and Mercury Racing 2.5 blocks and a few 2.0 and 2.4 Liters, too. The "double letters" are stamped on the port-side edge where the block halves meet, upper 1/3rd of the powerhead: EE KK SS PP LL FF NN

A high-performance boat propeller works by converting torque into thrust. Propeller blades are designed to displace water, to create the most efficient forces to lift and move the boat forward. As the propeller rotates, it pushes water backward, creating space in the front that water must rush in to fill. This creates a pressure differential that draws water into the propeller from the front and accelerates it out the back. The more air that is pulled behind the propeller, the more thrust or forward propulsion is generated. Balancing this with lift is critical to ensuring your prop design matches your boat and set-up. For instance, "natural lift" found in a Mod VP or Tunnel Hull design might allow the prop design to spend more energy pushing the boat forward, while a heavier v-bottom might require the prop to spend more energy lifting the boat. While the art of designing a propeller is fleeting, here are 8 design features that are the building blocks of a winning stainless steel propeller. They are the fundamental aspects of science, that we can tweak to find improvements.

This Mercury Marine and Mariner Outboard Decal Identification Chart can help identify the model year of an older engine by the decal design and colors on the cowl. The chart includes Kiekhaefer and Merc logos years including 1939-1945, 1946-1954, 1955-1970, 1971-1977, 1978-1998, 1999-2005, 1990–1993, and 1994–2000. You can also find the serial number and model number on an ID tag on the mounting bracket, or in some cases on an engine block freeze plug. The latest serial number labels display a 2-digit number in a box at the lower right portion of the label. These digits coincide with the last two digits of the year in which the outboard was manufactured. For Mercury 2.5 Liters, please see our info post with block identifications for all the double letter stamps such as AA, BB, CC, EE, FF, F, NN, SS, PP, LL, etc.

Cockpits, capsules, crash boxes, and safety cells are so important to the future of all forms of racing from Indy Cars to Formula 1 and offshore race boats. I’m not an expert on the subject so I did some research on the subject including the APBA and UIM testing procedures as well as the emergence of the 10k supercell. I think it’s important for everyone racing to share experiences and knowledge to move our sport into the future.

The ratio of fuel to oil in a two-stroke engine is expressed as a ratio. For example, a 50:1 ratio is 50 parts fuel to 1 part oil. This fuel-to-oil ratio is important for two-stroke engines because the oil lubricates the piston and seals the rings in the cylinder for optimal performance. If the ratio is too lean (not enough oil), the engine may not get proper lubrication, and damage to piston rings and bearings could occur. If the ratio is too rich (too much oil), it can result in smokey exhaust, fouled spark plugs, and excessive deposits in pistons and exhaust ports. The average ratio for two-stroke motors varies from 16:1 to 100:1. The most common ratios for higher-performance 2-stroke outboards are; 40:1: or 3.2 fluid ounces of oil per gallon of gas, and 32:1: 4 fluid ounces of oil per gallon of gas. Some boat racing applications call for 20:1. Once you have determined your proper fuel/oil mix, use this chart to measure out the proper amounts to keep your powerboat running strong.

A spark plug gap that is too small can cause the spark to not ignite the air-fuel mixture. However, a gap that is too large can cause the spark to be blown out at high speeds. The recommended gap for a high-performing 2-stroke outboard is between 0.030" and 0.042". However, manufacturers' recommendations for specific engines can vary. A good starting point is 0.035". You can experiment with different gaps to see what works best for your engine. A smaller gap ensures that the spark plug fires on each cycle. However, if the gap is too small, there is not enough room for the air-fuel mixture. If the gap between the electrodes of a spark plug is too small, the spark may be too weak to complete the combustion process. This can cause: Partial ignition Low power Misfires Spark plug fouling Increased plug wear Poor gas mileage A larger gap creates a longer spark arc, but it requires a higher voltage to fire. This can also put a strain on the ignition parts, such as the coil, stator, and wires. A spark plug gap that is too wide can cause the spark to lose strength as it crosses the gap. This can lead to: Engine hesitation A rough-running engine Misfires at high speeds A miss at higher rpm A loss of power Increased plug wear Poor gas mileage If the ignition system can't provide the voltage needed, or if turbulence in the combustion chamber blows out the spark, misfires will occur that decrease overall performance, ETs, and lap times. An engine runs best with the widest gap that the ignition can reliably fire. Spark plugs that are gapped incorrectly can cause an engine to miss or run erratically. Note: When gapping a plug be careful not to damage the precious metals tip, like iridium, platinum, silver, or ruthenium. Or weaken the j-gap by repeatedly bending open and closed while finding your ideal gap.

Here are some common wiring color codes for Mercury and Mariner outboard motors that are listed in this chart: Red: 12-volt hot Purple: Ignition on key switch and gauges Black: All grounds Light blue/white stripe: Trim up switch Light green/white stripe: Trim down switch Brown/white stripe: Trim sender to trim gauge Purple/white stripe: Trim "trailer" switch Tan: Temperature switch to warning horn Tan/blue stripe: Alternate color for temperature switch to warning horn Yellow/Red Stripe: Starter solenoid to starter motor Yellow/Black Stripe: Choke or Primer Fuel Enrichment Yellow: Charging Circuit from Stator Brown: Reference electrode MerCathode Tan/blue: Audio warning buzzer Gray: Tach

The objective is to measure peak AC voltage (adaptor converts to DC volts) at 6 key points in your Mercury V6 outboard ignition system. Before you begin, ensure you have a strong spark and good compression before proceeding to the Peak Voltage Tests (with the Buckshot Racing #77 DVA Adaptor). Plug the adaptor into your multimeter, set to read over 300 volts DC. Run tests stationary in a safe place, in the order listed on the chart, with grounds connected. Stay clear of voltage shocks and fuel. Test #1 is key. If you can confirm all cylinders read within the spec above and within a close range of each other while cranking, move to confirm in the same way with the motor running. Typically, we'll see 200 increasing to 220 volts while increasing the RPMs to around 3,500. If you get this far with passing grades, you have confirmed your ignition most likely has no other issues and it might be time to look elsewhere. Otherwise, continue to tests #2 to #6 until you pin point your problem.

Electrolytic Corrosion: Also known as stray current corrosion, this occurs when dissimilar metals are in contact with an electrolyte, such as water, and an electrical source. The result can be a rapid reaction that can cause significant metal damage in a matter of hours or days.​ Galvanic Corrosion: This occurs when two dissimilar metals are directly connected, causing the lesser of the two metals to corrode.​ Marine Corrosion: This occurs when the salt in air and seawater leads to the chemical degradation of exposed metal surfaces.​ Microbiologically Influenced Corrosion (MIC): This occurs when microbes are involved with corrosion.​ Anodes are designed to help prevent corrosion from happening. They are typically ​made of zinc, magnesium, or aluminum and are usually located on trim tabs.​

How to use a piston deck height tool with dual dial indicators (aka bridge gauge) to get accurate measurements of all piston heights on your Mercury Racing or Black Max V6 2.0/ 2.4 / 2.5 cylinder block to find the correct squish band (clearance) for maximum HP and motor longevity.

This powerhead wiring diagram is for the Mercury Racing 2.5 Liter Outboard with the Horn-style side-injected EFI​ system found on the 260 HP, 300 Drag, S3000, and ROS engines.

This powerhead wiring diagram is for the Mercury Racing 2.5 Liter Outboard with carburetors (carb) found on the 245 HP, SST-120, F200, and F1 race engines.