Interesting real world data.
Perception is also a good "stats bender". I use my own clamshell as an example.
Most people old enough to remember them - what were they notorious for? - Overheating & killing their top piston. So why did I choose one? The main reason (other than availability & budget) was the weight. My transom will only take 110 KG, a "bulletproof" Yam 60 auto mixing 2-T would have given me no capacity for an aux.
I got an engine that having dismantled it turned out to be a lot older than the cowl's paint job suggested. I found stuff that acording to the microfiche implies I had a late 60s (i.e very early) one. And guess why I rebuilt it..... yep, it destroyed it's top pistion!
So, I researched it and found a few changes:
Cooling - the entire Inlet side of the cooling system had been changed. The down side is it is over cools at idle so runs a bit rough down there, but I don't spend long enough "trolling" to care about that. Also the tell tale outlet was changed to about half the size (to direct a bit more water past the hot bits!)
Self destruct pistons - well.....
The new pistons inside my engine are a god few grams lighter than the originals, and also have 2 rings instead of three on the original. The spark advance has (officially - not just me tinkering!) been retarded by a few degrees (it was the pistons being pushed into the exhaust port seems to have been the main problem - and guess how mine died!) . the lighter pistons allow it to rev about 500 rpm or so higher than the 1960s version thus restoring the power lost by retardeding the spark.
Another famous fail was the standalone auto mixer. Guess why I premix!
I'm led to believe the newer vintage Clamshells were actually quite reliable - and certinly were a vast improvement compared to the older generations. .......
But all people rememeber is "they overheat and destroy the top piston...."
Which is Why frequently I type here "research - donlt jsut go by the rumours.
TBH I'd love a nice new quiet lightweight Yam on the transom & leave the dinosaurs as restoration projects.... but don't have that sort of cash lying around!