Mercury OptiMax 150 HP DFI Outboard Fuel Injector Cleaning & Flow Testing

The Siemens 37003 is a DFI marine (2-stroke direct injection) fuel injector used in Mercury 150 HP DFI OptiMax 2-stroke direct fuel injection outboard. We ultrasonic-clean and flow-test injectors like this one in our shop, then send back before-and-after data so you know exactly what you're getting.

Manufacturer	Siemens
Part number	37003
Type	DFI marine (2-stroke direct injection)

Get This Injector Serviced

Our measured results

These are the actual before-and-after numbers from our flow bench for the Siemens 37003 — not published estimates.

Tested in our shop	6 injector(s) @ 50.0 psi
Measured coil (avg)	2.2 Ω
10s open flow (avg)	85.0 → 84.0 ml (-1.2%)
60s pulsed flow (avg)	58.83 → 61.0 ml
Leak test after cleaning	6/6 PASS

Also known as / cross-references

The Siemens 37003 is interchangeable with or cross-references to these part numbers:

804841 (Siemens Deka OEM)

What vehicles use the Siemens 37003?

Mercury 150 HP DFI OptiMax 2-stroke direct fuel injection outboard

How we service it

Every injector gets ultrasonic cleaning, backflushing, before-and-after flow testing (static and dynamic), leak testing, spray-pattern inspection, and new O-rings and micro-filter baskets where available — plus a detailed Injector Performance Report. Round-trip USPS shipping is $15 flat.

Frequently asked questions

What vehicles use the Siemens 37003 injector?

The Siemens 37003 is used in Mercury 150 HP DFI OptiMax 2-stroke direct fuel injection outboard.

Can you clean and test a 37003 injector?

Yes. We ultrasonic-clean, backflush, and flow-test the Siemens 37003 on our bench, including before-and-after open and pulsed flow, leak testing, and spray-pattern inspection, with new O-rings where available.

What did the 37003 flow at?

On our bench, 6 37003 injectors averaged 85.0 ml open flow before cleaning and 84.0 ml after, tested at 50.0 psi.

How much does it cost?

Standard MPFI top-feed injectors are $30 each; side-feed, GDI, TBI and specialty injectors are $35 each. Round-trip shipping is $15 flat, 4-injector minimum.

How do I send them in?

Start an order on our Get Started page, ship your injectors to our Weymouth, MA shop, and we return them cleaned, tested, and documented.

Send in your 37003 injectors

Mail-in cleaning and flow testing with a full before/after report. 4-injector minimum, $15 flat round-trip shipping.

Get Started