Mercury Optimax 101

[InjectorService]

For those of you that don't know me, my name is Blake, and I own and operate Canadian Fuel Injection Service. We are a fuel injector cleaning & resting company specializing in outboard and and motor-sport products.

Onto the good stuff! This thread is something I have wanted to build here for a while, and the time is now. My plan is to use the first number of post spots for a general knowledge base on the Optimax motors. More specifically the VERY misunderstood fuel and air systems. I will be trying to organize the thread into groups based on specific areas and differences in the systems.

I DO NOT claim to know it all, so please, if something is wrong on here, or you have questions, feel free to PM me or reply to the thread.

Time for my business plug. If you need ANY Optimax parts, or a fuel rail/injector service, please PM me and I will try my best to help. I have good access to Merc parts and fairly cheap and fast shipping. I will say though, I don't carry a ton of used stuff on hand, but you can feel free to inquire as well.

Hopefully some of the powers that be can make this a sticky as it grows as well. It won't happen overnight, but I want to get this information out there.

Blake

Optimax General Information / Specs:
- Optimax are a direct injected motors, but are not very different to diagnose from a typical fuel injected system.
- There are 4 basic "sizes" or displacements of Optimax motors: 1.5L - Inline 3, 2.5L - V6, 3.0L - V6, and the 3.2L - V6 (300xs).
- All of the Optimax motors fall into 2 basic fuel system categories: 14psi & 10psi (more on this later)
- There are 2 different styles of VST: "Old" & "New" although that's not 100% accurate, its how I differentiate them.
- There are 3 main systems of injection on an Optimax, and they are all independent, sort of. Oil, Fuel, Air
- The oil system is a crankcase injected system, one oil pump, a number of lines, feed different bearings & areas of the block. (I'm not going to go much into the oil systems on these, yet at least)
- The fuel system is a basic fuel injection system, a lift pump, low pressure pump, high pressure pump, 1 injector per cylinder, and a fuel pressure regulator.
- The air system is essentially a basic fuel injection system as well, only with a compressor instead of fuel pumps, 1 injector per cylinder, and a pressure regulator.

Thats it. The above is an Optimax in a nutshell. The sooner you understand the above, and treat all the systems separately, the sooner you will be an Opti Master. The sooner I'm out of a job.

[InjectorService]

There are 4 colors of Optimax fuel injectors. (don't confuse these with the AIR injectors)

They are:
- Purple - Early V6 I believe 135 & 150 only. Not very common, but I have seen them around
- Red/Burgundy - Very common - all 1.5L, 3.0L, 3.2L, most 200XS 2.5L, 2.5XS, 150 ProXS
- Yellow - I've never seen these in person, I believe they inject sideways, I don't believe there are any of these motors in existence any more. I believe these were only on the VERY early 200hp. I don't think they sold the fuel injectors separate either. If you have any of these laying around please send them to me, I would like to check them out in person.
- Black - MOST 2.5L there are some exceptions that use purple or red (see above).

Fuel injector colors are NOT interchangeable. If you had red, stick with red, if you had black stick with black etc. they DO have different flow rates.

If you don't know what your motor was supposed to have in it for some reason, I would look it up by serial number, especially for some of the high performance 2.5L motors. There were serial number breaks in some cases, that changed from black, to red.

Also, if you change your ECM, you MAY need to change your injector color for air and/or fuel, as well as your fuel pressure regulator.

https://i.postimg.cc/wj0tNs8z/Fuel-Injector-Colors.png (https://injectorservice.com/)

- As far as injectors go, these are basic side feed injectors made by Siemens Deka.

[InjectorService]

Ok, now we are getting onto the SCARRY stuff, air injectors! What on earth is an air injector? Well, its simply a fuel injector, a direct injector to be exact.
- Mercury reffers to these injectors as 2 things; Direct Injectors OR Air Injectors - They are the same, no difference, just a different way of describing them.
- The automotive industry refers to this style of injector as Direct Injectors OR GDI Injectors.
- The injectors are mounted in the cylinder head, and spray DIRECTLY into the combustion chamber, thus the name.
- The injectors seal into the cylinder head using a teflon sealing ring, the rings are reusable, unless damaged.

[InjectorService]

Reserved for Optimax fuel pump / VST information.

[InjectorService]

Reserved for Optimax Air Compressor information.

[InjectorService]

This post reserved for fuel rails.

[rock]

Need to bring this back up

Rock

[InjectorService]

You're right I should definitely finish this up. If you have anything specific you want to see let me know.

[xcheesehd]

Right on Rock!!!