Monitoring exhaust gas temperature (EGT) and RPM is critical when tuning and maintaining Mercury 2-Stroke V6 outboards, especially in high-performance racing environments. These metrics provide insight into combustion efficiency, timing accuracy, ignition issues, lean conditions, and potential overheat conditions.
The Koso EGT-02R EVO digital dash, integrated with custom sensors and installation hardware developed by Buckshot Racing #77, delivers a robust and precise solution for real-time EGT and RPM tracking.
This guide outlines system components, features, installation, and technical specifications for Mercury 2.0L, 2.4L, and 2.5L V6 outboard engines.
System Overview
The Koso EGT-02R EVO gauge is a fast-response, dual-channel digital gauge designed to monitor exhaust gas temperatures on both port and starboard banks of V6 engines. It includes:
Real-time RPM display
Max temperature recall
°F/°C temperature units
Data logging for up to 50 recorded sessions
Configurable warning thresholds for EGT, voltage, and RPM
The system interfaces with high-speed Type K thermocouples and is designed for the harsh vibration and thermal loads typical of 2-stroke marine racing.
Kit Components
1 x Koso EGT-02R EVO dual EGT gauge
1 x Mounting bracket and vibration-resistant hardware
2 x BlaZen Fast EGT probes (Type K)
2 x 18-foot braided stainless Type K extension cables
2 x Stainless Steel Rifle Bolt Kits for exhaust divider installation
1 x Temperature Sensor (short lead, requires customer extension)
1 x Tachometer signal wire (short lead, may require customer extension)
BlaZen Fast EGT Probes
Developed alongside a thermocouple specialist, these probes provide highly responsive and durable measurements:
Type K, Special Limit of Error: ±1.1°C or 0.4%
Sheath: Inconel 600 for extreme temperature resistance
Junction: Exposed, with optimized bead size for fast feedback
Geometry: 90° bend, 4" hot leg, 1" cold leg
Wire: 12" FEP-insulated 20 AWG, stainless steel overbraid
Termination: Mini K-type plug (flat pin)
These probes are installed using stainless steel rifle bolts with compression nuts, specifically designed to replace the lower bolt holes of Mercury V6 exhaust divider plates.
18-Foot Thermocouple Extensions
Built for marine-grade durability, these extensions connect the probes to the dash:
Conductor: 20 AWG stranded core
Insulation: PTFE (Teflon)
Shielding: Full braided stainless steel overwrap
Connectors: Mini jack to mini plug
Length: 18 feet
For best performance, route these through the gunnel, away from the bilge or other high-moisture zones.
Koso EGT-02R EVO Gauge Functionality
EGT Channels: Dual inputs for L/R cylinders with independent warnings
RPM Input: Live RPM display from signal or inductive pickup
Max Temp Memory: View and reset peak EGT for each channel
Data Logging: Records up to 50 separate engine runs
Units: Switchable °F/°C
Voltage Monitor: 8.0–18.0V with high/low threshold warnings
Backlight: 5-level adjustable brightness
These features allow racers to detect detonation, lean conditions, or dangerous voltage climbs during operation.
Installation Guidelines
EGT Probe Installation
Use two lower bolt holes in the exhaust divider plate
Install rifle bolts and secure probes with brass ferrules and compression nuts
Position the probe junction ~1/4" into the tuner passage for optimal gas sampling
Routing Extension Cables
Use the included 18-ft Type K braided stainless cables
Avoid routing near ignition or AC power cables
Secure inside a dry rigging tube using marine-rated zip ties or clamps
Extending Tach and Water Temp Leads
Both sensor leads are supplied short and must be extended for installation:
Tach Signal Wire
Use shielded marine-grade 20–22 AWG wire
Connect to the gray wire from the switchbox or regulator/rectifier (1 pulse/rev)
If unavailable, wrap the tach wire 3–5 times around a spark plug wire for inductive pickup
Solder all joints, seal with heat-shrink, and route away from interference
Water Temperature Sensor Wire
Extend with twisted-pair or shielded cable
Install the sensor in a head plate, top block, or divider plate tap
Use marine-grade waterproof connectors for reliability
OEM Compatibility & Replacement Notes
This system is designed to fully replace these discontinued Mercury Racing components:
EGT Kit #91-847564A2
Meter #91-8475642
Probe #847558A1
Wire Assembly #84-847562A1
Additional accessories, tools, and ferrules NLA from Mercury
For Mercury Racing 2.0L, 2.4L, and 2.5L 2-stroke V6 outboards, this EGT and RPM monitoring kit offers precision measurement, real-time visibility, and durable marine-grade construction. When tuned properly, these insights protect your engine under extreme loads and enable optimal performance on the racecourse.
Combine your VBOX with our Kit and ditch the expensive and cumbersome AIM Sports system.
For install help, downloadable manuals, or additional support, visit our Tech Hub or contact:
Mike Hill – Buckshot Racing #77
📞 +1-714-697-1716
✉️ mike@buckshotracing77.com