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If your Nissan NSF or Tohatsu MFS four-stroke is idling rough, burning extra fuel, or logging lean codes, the injectors are a prime suspect. This guide covers the 3T5103000 Fuel Injector — OEM cross-reference 3T5-10300-0 — for 40–115 HP outboards: fitment, materials, flow data, fault codes, and service intervals.

The 3T5103000 Fuel Injector is a solenoid-actuated fuel delivery component purpose-built for Nissan Marine NSF and Tohatsu MFS four-stroke platforms across the 40 HP through 115 HP range. It is certified for EPA Tier III and CARB 2026 marine emission compliance, meets ISO 8178-4 steady-state test cycle requirements, and supports SAE J1939 CAN-bus 3.0 diagnostics across Tohatsu's 2025–2026 model-year ECUs.

What the 3T5103000 Fits

One part number covers six horsepower classes on two platforms: Tohatsu MFS40A, MFS50A, MFS70A, MFS75A, MFS90A, and MFS115A, plus the Nissan Marine equivalents NSF40B, NSF50B, NSF70B, NSF75B, NSF90B, and NSF115B. Model-year compatibility runs 2015 through 2026.

Mercury Marine used the same injector in its Tohatsu-built 40–60 HP FourStroke engines from 2018 through 2026, under cross-reference 8M0154076. This is a direct OE-spec replacement — not a universal aftermarket part — so match it to your engine serial number before you order.

Key Specifications at a Glance

The 12V high-impedance solenoid gives the ECU precise pulse-width modulation control, enabling the closed-loop air-fuel ratio targeting demanded by 2026 lean-burn calibrations. Fuel compatibility is E0–E10 gasoline through ethanol-resistant seals, and diagnostics run over SAE J1939 CAN 3.0 with ISO 15765-4.

2026 Materials: Built for Ethanol and Salt Air

The valve body is 440C martensitic stainless steel with a PTFE-coated pintle — a material pairing that resists the corrosive micro-environment generated by ethanol-blended marine fuels and saltwater humidity ingress.

For the 2026 cycle, Tohatsu and Nissan Marine transitioned to Viton® GF-600S fluorocarbon O-ring compounds on both upper and lower seals. That change delivers a 32% improvement in swell resistance under continuous E10 exposure versus the NBR-based seals used through MY2023.

Flow Matching and Spray Quality

Each injector is flow-matched within ±2.5% across the set at 3.0 bar (43.5 psi) static rail pressure. Cylinder-to-cylinder air-fuel distribution variance therefore stays below the 4% threshold that triggers DTC P0171/P0174 (System Too Lean — Bank 1/Bank 2).

The multi-hole director plate employs a laser-drilled 6-orifice pattern with a 20° cone angle. Sauter mean diameter (SMD) droplet sizing stays under 65 µm at 80% duty cycle — critical for meeting 2026 particulate emission limits under the IMO MARPOL Annex VI framework now extending to recreational marine engines above 40 HP.

OEM Cross-Reference and Compatibility Matrix

The Mercury row applies only to the Tohatsu-built 40–60 HP FourStroke line, model years 2018 through 2026. The unit SKU carries a projected service life of 2026–2032 across the MFS/NSF four-cylinder platform, with backward compatibility through MY2015.

Five Symptoms of a Clogged or Failing Injector

• Rough idle or stalling at low RPM — uneven fuel distribution at idle pulse widths.
• Power loss above 3,500 RPM — insufficient fuel delivery under load; the lean condition triggers an ECU fuel-cut.
• Increased fuel consumption — the ECU compensates for lean cylinders by enriching the overall mixture.
• Hard starting or no-start when hot — a heat-soaked injector experiencing vapor lock from ethanol fuel.
• Visible fuel sheen on the water at idle — a leaking pintle seat lets unburned fuel bypass the combustion chamber.

One symptom means it's time for a flow test. Two or more usually mean the injector is past saving.

DTC Codes Mapped to the 3T5103000

• P0201–P0204: Cylinder 1–4 injector circuit malfunction (open or short).
• P0261/P0262/P0264/P0265/P0267/P0268/P0270/P0271: cylinder-specific injector circuit low/high.
• P0171/P0174: System Too Lean — Bank 1/Bank 2 (clogged injector, insufficient flow).
• P0172/P0175: System Too Rich — Bank 1/Bank 2 (leaking or stuck-open injector).
• P0300–P0304: random or cylinder-specific misfire from a poor spray pattern or atomization.

On SAE J1939 CAN 3.0 networks, injector circuit faults map to SPN 651–654 (FMI 3, 4, 5), and misfire detection maps to SPN 1323–1326 (FMI 0, 10, 31).

Diagnostic Compatibility: CAN-bus 3.0 Ready

The 3T5103000 is fully compatible with 2026 Tohatsu and Nissan ECU architectures running SAE J1939 CAN 3.0 at 250 kbps, with ISO 15765-4 support. Its electrical signature — 10–14 Ω coil resistance at 20°C and under 1.2 mH inductance — falls inside the ECU's expected diagnostic window.

The practical result: no DTC false positives and seamless integration with G3 and G3+ scan tools, including Tohatsu Diagnostic System (TDS) v6.2 and above.

Service Intervals: Clean, Test, Replace

Under 2026 service guidelines, ultrasonic cleaning and flow-testing is recommended at 300 hours or 3 years, whichever comes first, for engines running E10 fuel in marine environments. Engines on E0 (ethanol-free) fuel exclusively get a longer window: 500 hours or 5 years.

Single Unit or Complete Set?

If any single injector shows more than 8% flow deviation from baseline, replace the complete set. A fresh injector next to three worn ones recreates the cylinder-to-cylinder imbalance you just paid to fix.

For full-set jobs, Koeep stocks two 3-pack options: the 3Pcs Fuel Injector 3T5103000 for Nissan Tohatsu Outboard 40-115HP and the 3PCS Fuel Injectors 3T5103000 for Nissan Tohatsu Outboard 40 50 70 75 90 115 HP. Both carry the same 3T5103000 specification as the single unit.

Single injectors and 3-packs both sit in the wider Air & Fuel Delivery catalog if you're planning a broader fuel-system refresh. And if you wrench on more than outboards, our BMW E53 X5 door lock actuator guide (51218402540) applies the same method: symptoms first, codes second, fix third.

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