Mercury OptiMax Injector Cleaning Service

Mail-in cleaning and flow testing for OptiMax air and fuel injectors. Ship from anywhere in the US.

OptiMax injectors run our bench constantly. They are one of the most common marine injectors we service, and one of the most misunderstood. An OptiMax that starts hard, idles rough, or falls on its face at wide-open throttle very often has nothing wrong that a proper cleaning and flow test will not find.

We clean and test both the air injectors and the fuel injectors, individually, and send back a report with real numbers for every one. $35 per injector, $15 round-trip shipping, 1 to 3 business day turnaround once they hit the bench.

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Why OptiMax Injectors Are Different

OptiMax is a two-stage direct injection system. The fuel injector meters fuel into a charge chamber, then the air injector fires compressed air (about 80 PSI off the belt-driven compressor) to atomize that fuel charge and drive it into the cylinder. Two injectors per cylinder, twelve total on a V6, and the system only runs right when both stages are healthy.

That design has two consequences for cleaning:

  • Half-cleaning does not work. Cleaning the fuel injectors while the air injectors are gummed up (or the other way around) leaves the engine misfiring the same way it did before. When an OptiMax comes to us, we want the full set.
  • Dock-side testing tells you almost nothing. OptiMax fuel injectors are low-impedance coils, right around 2 ohms. A multimeter says "not dead," and that is all it says. Whether an injector is delivering its full fuel charge evenly can only be measured on a flow bench.

These injectors are also getting expensive and scarce. New replacements run $150 to $250 or more each when you can find them, and Mercury has discontinued several part numbers. Keeping a good set alive with proper service is by far the cheapest way to keep an OptiMax on the water.

Real Numbers From Our Bench

This is an actual set of six OptiMax fuel injectors we serviced recently, from the same report the customer received. Not a stock photo, not marketing numbers.

Test (6 injectors, 50 PSI) Before After
Average pulsed flow 58.8 ml 61.0 ml
Average open flow 85.0 ml 84.0 ml
Pressurized leak test 6 of 6 pass 6 of 6 pass
Average coil resistance 2.2 ohms (healthy low-impedance spec)

This particular set came in reasonably healthy and still picked up almost 4% in pulsed flow, which is the measurement that matters most for how an injector behaves at real operating duty cycles. Just as important, the report proved all six sealed under pressure and flowed within a tight spread of each other. That is what you are paying for: not just cleaning, but knowing.

Siemens Deka 37006 Mercury OptiMax fuel injector on our bench
Deka 37006 from a Mercury 135 OptiMax, on our bench
Siemens Deka 37003 Mercury OptiMax fuel injector on our bench
Deka 37003 from a Mercury 150 OptiMax

More of our recent marine work, with measured flow data, is on the Recently Serviced page.

OptiMax Engines and Part Numbers We See

We service injectors from every OptiMax DFI outboard, 1998 through the end of production, including Pro XS models and the SportJet 200 DFI. The fuel injector part numbers we see most:

Part Number Type Common Applications
Deka 37006 Fuel injector Mercury 135 HP OptiMax DFI, SportJet 200 DFI
Deka 37003 Fuel injector Mercury 150 HP OptiMax DFI (also seen on 175)
804841 (Siemens Deka OEM) Fuel injector Mercury OEM cross-reference for the Deka DFI family
OptiMax air injectors Air injector All OptiMax DFI models, two-stage direct injection (send these too)

Not sure which injectors your engine has? Email us a photo or your engine serial number before shipping and we will confirm.

What the Service Includes

  • Ultrasonic cleaning and backflushing, air and fuel injectors
  • Individual flow testing before and after cleaning at 50 PSI
  • Pressurized leak-down test on every injector
  • Coil resistance check
  • New O-rings and filters where available
  • Written performance report with per-injector numbers

$35 per injector, air or fuel. $15 flat round-trip shipping.

A set of 6 OptiMax fuel injectors: $225 total. The full 12-injector set from a V6 (6 air + 6 fuel): $435 total. Compare that to $150 to $250 each for new injectors, when they are even available.

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OptiMax Questions We Get

Should I send my air injectors and fuel injectors together?
Yes, if you can. OptiMax direct injection depends on both working together, and cleaning only half the system leaves half the problem in the engine. Bag air and fuel injectors separately and label them. If you only send one type, we will clean and test what you send, but a full set gives the best result.
Is cleaning worth it, or should I just buy new injectors?
New OptiMax injectors typically run $150 to $250 or more each, and several part numbers are discontinued or getting hard to find. Cleaning is $35 per injector, and the flow report tells you exactly which injectors are back in spec and whether any are beyond saving. Most dirty injectors come back to spec. If one is truly dead, you only buy the one you need instead of a full set.
What's the turnaround time?
Most sets are cleaned, tested, and shipped back within 1 to 3 business days of arriving at our bench. Round-trip shipping is USPS Ground Advantage with a prepaid label we send you, so total door-to-door time is usually about a week to a week and a half depending on where you are in the US.
What does the flow report actually show?
Every injector is tested individually before and after cleaning: coil resistance in ohms, open flow, pulsed flow at operating pressure, and a pressurized leak test. You get the numbers for each injector, not just a pass or fail. OptiMax fuel injectors are low-impedance, around 2 ohms, so a resistance check at the dock tells you very little. The flow bench is what shows whether an injector is actually delivering fuel evenly.

Related Reading

Mercury OptiMax Cleaning Guide

The full walkthrough of how we clean OptiMax air and fuel injectors, step by step.

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Outboard Running Rough? 7 Causes

Marine mechanic's diagnostic guide, what to check before tearing into anything.

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Recently Serviced Injectors

Real injectors from our bench with measured before-and-after flow data.

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Flow Testing Process

How we individually test every injector before and after cleaning.

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