I agree "full flow" - but IMVHO there's still needs to be some, which is enough for flushing purposes.
Regardless, I still consider it good practice to do what you can - even if the block and heads don't get as much flow through as you'd like.
I guess more modern hi tech outboards have a diverter syle stat - so most of water circulates through the engine when stat is closed to maintain a good and even operating temperature - emissions etc.
Chryslers - I can hear the sound of them now - they always had a particular mechanical sound to them. But yes, the washer was key to maintaining some adequate pressure on the Merc V6s. In this day and age, I can't imagine running without a thermostat - outboards are so good these days. Long way removed from the days of my fathers oil slick seagull that ran 10:1 and used engine oil.
I saw the guy at Beeston mechanic yesterday briefly and asked him if he'd bother flushing after putting it in the Trent. He said it's freshwater and it's flushing itself by motoring in it, don't bother .
I'll still give it the occasional flush I reckon, couldn't hurt it, 'cos mud, silt and sand are real things.
My new yamaha 4 stroke had a flushing port with a hose lock type attachment. It was very clear in the manual and explained by the dealer, that the port was for flushing, not running the ob. I assume that yamaha wouldn't be stupid enough to install a flushing port that only flushed up to the thermostat and didn't flush the head or block. I'm not sure how this worked, but they are probably the Premier manufacturer of ob's, I doubt they would have overlooked this!
I have also got a set of muffs, but I find the telltale isn't as strong with these compared to a bucket. Which makes me think they aren't delivering enough water. I prefer a bucket. I brought a huge plastic plant pot from b and q for less then 20 quid and use that. It's bigger than a builders bucket.
Used to use muffs on the main engine (135hp) & a dustbin for the 4hp to flush.
Bought a big plastic storage bin on wheels off Amazon to do the main early this year as I had some problem solving to do which was likely to take a few days.
Couldn't use a bongo or a dustbin due to the permatrim on the cavitation plate.
No constant stream of dirty water (2 stroke) flowing down the drive & it's also a lot quieter.
I use muffs and flush for 10 mins after saltwater use. I used to use the flush port on a honda bf6 but the hose used to come off sometimes. I don't flush after fresh water use but I was told it is a good idea because it will get rid of silt
. 
