I wouldn't have thought so John. I've never done water injection on a 7 as I'm mainly 60Hz. For a 5 or a 6 there is no problem. Who is telling you need MKIVe.
Does anyone else have any input here who are more familiar with MS7001?
I don't think we have the whole story, but that's not the relevant point.
The relevant point is that GE doesn't support modification of Mark IV inputs and outputs (hasn't for years), and the current version of Water Injection requires a milliamp output signal to the variable frequency drive which powers the pump. And, the flowmeters would require either milliamp- or TTL inputs.
Also, programming the Mark IV to use a Wet Low NOx algorithm is not supported either.
Your question is "is it a must?". All the answers here so far are correct in that it is not supported, no algorithm etc. However to be specific the answer is "no it is not a must". However one must answer the "how" question. From my past experiences, (I have worked with GE and done it on my own) I have used external PLC's or offloaded the task to the plant DCS. Most recently Steam injection to augment power and reduce Nox on a Mark II system was handled by the plant DCS.
