I notice you differentiate between a Detroit Tech and a Detroit Surveyor. Wouldnt a Detroit Tech be the one to do the survey? Is there a different type of Tech that you would have survey it?
Pending your environment (the swamp or S Florida);
These two jobs can be preformed by the same guy or entirely different guys. Sometimes from the same shop, sometimes not.
Here in the swamp, Bubba does it all.
A tech/mechanic fixes things.
An engine surveyor inspects things.
A real tech/mechanic has already lost his hearing.
An engine surveyor's ears are not usually blown out (yet) and can hear that lil ticking sound better. He also carries a sound level meter.
A real tech/mechanic makes more money fixing things.
An engine surveyor rarely gets his elbows dirty.
Some tech/mechanics look to get that emergency repair work he supposed to have just discovered.
An engine surveyor rarely gets his elbows dirty.
Most tech/mechanics are not marine engineers.
An engine surveyor may have some marine engineering background; Proper engine installation, proper sized/design propeller, proper engine room ventilation. He may also work with the ship's surveyor better investigating & deeper into umbilical options, hoses, wires, exhaust, fuel & fire control.
I just did an internet search for these examples. I am not suggesting any of them but to just highlight that they are out there;
https://krugersurvey.com/
https://www.outboardenginesurvey.com/
https://www.flmarinesurvey.com/
https://dieselsurveyors.com/