My opinion is that this is a "marketing ploy" more than an actual benefit.
These wash out ports have been around for a while and some people use them, but most people either ignore them, don't know their purported use, or don't care (about maintenance) anyhow.
If..........a person uses the port as it was intended by the original designers, it might actually help remove some of the clippings thrown against the deck shell.
But "use as intended" means that the deck must have already been clean before you cut the lawn, and then just as soon as you make your last run with the blades spinning........you go immediately to your pre-selected wash out site (hopefully concrete or asphalt paved) and connect the hose (that you already had hooked up and waiting).
Then with the water running full blast, you sit on the machine (safety interlocks, remember) and engage the blades while running the engine at full open throttle. Use a timer and run the machine like this for at least 2 minutes.
And then you might have removed at least some of the clippings.
Then you unhook the hose and put it away, get back on the machine and drive it off.
Ideally at this point you will park the machine inside a building and place a small electric fan to circulate air under the deck (raised to its full up position) to dry everything out (maybe).
Introducing a spray of water to the underside of a mower deck in this fashion is more of a "pat yourself on the back", "gee what a good boy am I" type of gesture (once again, IMHO) than anything loosely related to maintaining the deck system.

This post was edited by mownie on Tue, Apr 16, 13 at 0:26

My mower has the hose connections on it also.

But the manual that came with it say's to never use water to clean the deck. It say's to used compressed air only!

Go figure!

When I got my used ZTR,. the owner of the shop delivered it. He said never get it wet, but use lots of compressed air on it, pulleys, cooling system , etc.

I never use mine but I do take off the deck and pressure wash it all out from time to time.Never had a bearing issue and feel if I did not do this I would have a rotted out deck long before a bad bearing.