ON A 1997 EVENRUDE : tilt motor up and remove "P" hole plug .Connect fresh water hose ,turn water on ,flush for 10 to 15 min. turn water off and disconnect fresh water hose, reinstall "P" hole plug. Leave motor in up pos.
On my twins I made a 'Y' hose adapter which has a quick disconnect to fit on each motor and the hose screws in the input side. I attach the hose and let it run for a good 20 mins or so and both motors are flushed at the same time.
I have to say I've never flushed an outboard in 45yrs. My boats have always stayed in the water. The only time they saw freshwater was when I winterized... I've never had a corrosion problem in that time because the engine wasn't flushed. Then again they've all been OMC or Mercs, well my brothers owned the Mercs..
On the flip side if you own a Yam or Zuke I'd flush it. They don't have the aircraft quality alum we have here. Yams are known for packing up the cooling jackets and popet valves with salt crud. Zukes until a few years ago just disolved in saltwater, but they seem to be much better than they used to be.
This year for the first time I'm banking on a Yam for the summer. It's a 95 150 ProV on the Key Hopper. I'm pretty sure Jaws changed the water pump in last year, but we both have been so busy this spring I haven't had chance to ask him what he did to the engine. Anyway I have to figure out how to handle this Yam if I leave the boat in the water.
BB, I'll be up next week for 8-10gals of XD50 and some Etec gearcase lube.. Run this Yam on the good stuff...