Yamaha F300, F350 V8 and XTO F375 to F450 Diagnostics by App

If you've got twin F300s or an F425 XTO on the transom, you don't want to guess when a warning comes up offshore. This class has the biggest ECUs in the lineup, with up to 65 live values and more than a hundred stored fault types. M-JET DIAGNOSTIC reads them at the diagnostic connector of each engine, over Bluetooth on your phone, with no laptop on board.

Models and ECUs

Covered are the F275B, the F300 in versions B, C, D, F and G, the F350 V8 as A and B, and the XTO models F375A, F400A, F425A and F450A, each also as a counter-rotating FL version. The twelve ECU variants deliver 30 to 65 live values, know 44 to 107 fault types and offer 16 to 25 actuator tests. All twelve support idle learning. Exactly what's available depends on the ECU generation, meaning the year the platform was introduced.

What the direct-injection XTO adds

ECUs with direct injection bring their own readings: DI fuel pressure separately for the port and starboard bank in MPa, vapor separator (VST) pressure in kPa, and the relays for the VST pump, low-pressure pump and the EDU, the driver unit for the injectors. Matching actuator tests cover the VST pump (main and sub), the low-pressure pump and both DI high-pressure pumps. Two functions come in handy when working on the fuel system: purging air from the fuel system after a filter change, and lowering DI fuel pressure before you open a line.

What the V6 and V8 share

• Intake cam angle and OCV separately for starboard (S) and port (P)
• Ignition coils and injectors one at a time, up to cylinder 8 on the V8
• Oil pressure in kPa, engine temperature, and on some ECUs cooling water temperature per bank
• two knock sensors instead of one
• ETV with TPS1 and TPS2, accelerator position sensors APS1 and APS2, digital shift with SPS1 and SPS2
• Starting and accessory battery voltage

Faults you only find here

On top of what the smaller classes log, the ECU here knows charging system faults where no signal comes from the generator. The checks then cover the wiring between ECU and rectifier/regulator and to the crank position sensor. Add the water pressure sensor, fuel pressure sensor, power supply for the shift actuator and VST pump, the trim relays and communication with the fuse box. The XTO also has its own entries for DI fuel pressure and DI pump per bank, the EDU power supply, and an irregular signal on each individual injector from 1 to 8. The check steps are mostly the same: inspect wiring and connectors, fire the injector in the stationary test, check the EDU.

Several engines on the transom

On twin and triple rigs you read each engine on its own. Comparing them often tells you more than any single value: if the port engine shows clearly lower oil pressure than starboard at the same rpm, you know where to look. What the data won't replace is a visual check of impellers, anodes and gear oil. On offshore boats in saltwater, those are the spots that give trouble first.

Related topics

• Yamaha Outboard Variable Cam Timing (VCT): OCV and Cam Position Sensor
• Diagnosing Yamaha Outboards on Twin and Multi-Engine Boats
• Yamaha HPDI Z150, Z175 and Z200 Diagnostics: Reading the Two-Stroke V6 by App
• All Yamaha outboard diagnostics topics

Everything runs via app over Bluetooth, for Yamaha outboards with control unit generations from 2003. Learn more about the M-JET DIAGNOSTIC for Yamaha WaveRunner & Outboard.