Save your 92s
There is lot of reading out there you need to do before changing injectors and props. To help you along on this, May I save you some time; DO NOT change the injectors or props.
Slowing down will save fuel. However keep in mind, The 92's are big, hold a lot of coolant, move allot of sea water thru them. They were built and designed for H P. At a fast idle, they will not come up to proper temperature and fuel burns in the cylinders may not be complete.
We run our 12v71TIs at fast idles around 10 knots. Every couple of hours, I'll lean on one (14-1500 rpm) for about 10 minutes. It stinks for a few seconds but the temp comes up, exhaust clears and I know the rings, pistons and cylinders are clear of unburned fuel and slobber, Then I idle that one back down and lean on the other for a few minutes. Doing one at a time puts a nice load on them and temp comes up in just a few minutes. Boat may speed up a knot or two and the pilot keeps the course straight.
We can not afford to pour diesel into our motors but during our two week vacations we cover some latitude. We have to run for 10, 15 and once 20 hours this way on legs from Jacksonville FL to the Bahamas and back. Engine oil stays clean.
One night we timed the current / wind wrong at Ponce Inlet (south of Daytona FL). It was real nice to have all 1300 H P on line when we needed it.
Slow down. Care for your engines. DON'T de-tune.
An old phrase I remember;
L S D; Low Speed Displacement.