In rough water the throttles are pulled back just before the props exit a large wave & powered up when the props pierce the next wave. All the props (twins or triples, or what have you) are unloaded & loaded in this manner...no matter which drive leaves last or enters first.
45% work load for the center drive seems excessive to me. Although I can neither prove or disprove it.
I can hazard a guess that port & starboard power used transmissions for docking purposes, while the center only needs the more simple, durable crash box. All very interesting......

I try to not get out of the gas until the props have just left the water, then only back half way or so depending how fast. Then gently back in to the gas just before re-entry, matching prop speed with water speed. Keeps the boat flying level and the transom up in bigger water.
It seems depth alone on a center drive would be a big factor. Need someone with a triple to chime in about center drive/engine reliability.

How about a guy with a big power single! It's for damn sure his center drivetrain is getting 100% load. Lol!! A good throttle man can really save the equipment. All good conversation. i hope Kemosabe chimes in.

One of the 41 sabers has triple number 5's and he has not seen any more wear and tear on the middle one than the other drives or motors Never know whats happening inside but everything gets serviced the same.

NK

As for throttling a boat the trick is to maintain rpm while topping the waves as far as I am concerned but thats just my opinion

Let's have a look.....a big Apache race boat with triple engines in some rough water.....
http://www.youtube.com/watch?v=niwjMgDl02k