Russell Borogove has already answered, but I wanted to point out more explicity a few things:
- ISP is a derived quantity
- You do not need to add any efficiency factor
- If the thrust and ISP figures come from the same test, by doing Thrust/ISP you are recovery the exact fuel mass flow measured at that test
I do not think you need to add any efficiency factor at all.
Specific impulse (usually abbreviated Isp) is a measure of how
effectively a rocket uses propellant or jet engine uses fuel. By
definition, it is the total impulse (or change in momentum) delivered
per unit of propellant consumed  and is dimensionally equivalent to
the generated thrust divided by the propellant mass flow rate or
weight flow rate. 
So $$ISP = Thrust / mass\ flow\ rate$$ and this means $$
mass\ flow\ rate = Thrust / ISP$$
So your calculation in the related answer is perfect.
One might wonder if this relationship is just theorical and if in reality some efficiency or other factors would apply when these three variables are measured.
As Russell Borogove pointed out, ISP is related to the exhaust velocity in an ideal abstract rocket, but more properly ISP is actually the effective exhaust velocity, which might be different from the velocity that you'd measure at the exhaust.
For example, in jet engines, the effective velocity will be higher than the exhaust velocity because they get "free oxygen" that contributes to thrust beyond what the fuel mass they carry would do with that exhaust velocity.
So how would you measure ISP/effective velocity in pratice?
From what I gathered so far, I guess that you do not measure ISP, you derive it from the other two quantities.
For sure when testing a rocket engine you can measure its thrust in a load cell and you can measure the fuel you are using running the engine (,)
So if those 7,607,000 N thrust and 162s ISP numbers come from empirical measurements done in the same session (and they are not estimates from simulations or calculated in another way), it is much likely that thrust was measured along with fuel mass flow and impulse derived simply by dividing thrust by fuel mass flow.
So when you do 7,607,000 / 162 you are really recovering the fuel mass flow measured in that test.
In this case, your fuel mass flow already accounts for any "inefficiency" or fuel that did not contribute to thrust, since it is the thrust obtained divided by the fuel really used (regardless if it was efficiently used or not).
Disclaimer: I never tested any rocket engine nor any other engine, this was just guesswork - however, this quora answer agrees: https://www.quora.com/How-do-we-measure-rocket-thrust-like-specific-impulses