Yes, the flushing port can be used to run the engine. Water pressure should be limited to 20psi max, and the engine should not be run at more than a fast idle, say ~1000 rpm.
I have the same situation here at work. We have to run our Rescue Boat engines for 6 min each week. The boat only gets run in the water about once every 3 months.
We just received twin brand new 75 HP evinrude E-Techs 2 strokes. We previously would run our engines with rabbit ears. Now the new engines have the flushing port, and we got the quick connect couplings for this.
Is it better to run the engine with the flush or the rabbit ears? My concern with runing the engine with only the flush weekly is that the water pump isn't sucking through the water intake on the lower unit and pumping out through the "pee hole" as designed. Eventually damaging the water pump possibly??
In the user manual it says "it is NOT necessary to run the engine for a good flushing" through the flushing port. So I feel like they kind of discourage it.
Then in the user manual it talks about flushing with the Gearcase Flushing device which would be the "rabbit ears." It sasy to take off the propeller for this, I'm assuming they only mention this as a safety pre-caution, but we dont put the boat in gear when we run it on deck and taking the propellers off every week would be impractle.
Any advice on this?
Only downside I see to using the flushing device is that the motor may not reach full operating temperature.
On the plus side you don't have to worry about the muffs slipping, & sucking air into the waterpump.