Times are a changing, I see the 200 HP Verado and Optimax are within 5 lbs of each other now. No way would I go back to a 2-S for five pounds of weight. As far as weight to giddy-up ratio, that's a changing too. There will be 4-S with every bit the snap of a 2-S in the not so distant future, that's where all the R&D money is being spent...not on making 2-S any better.
As far as Y vs M, I've run both. Given my d'ruthers...I'd take a Yamaha just about every time. They can all have their problems, but in my memory bank it's been Merc with the systemic issues, especially in the Opti series a few years back. My old(er) Yammie keeps on a purring (granted, it's a 2004 model, so a Merc of the same generation runs the same powerhead), but I just watched a newer and unabused Merc discombobulate on the back of my Toon last year. A little over $9k of Merc warranty to put a new powerhead on got me back up and running again, but now I have trust issues again with Mercs.
Truth be told though, all of the outboards nowadays are just light-years beyond what I knew outboards to be back in the 70s and 80s. Take care of them and they should all last a couple thousand hours. And for most of us, that's a lot of years on the water!
Weight comparisons:
Merc Proxs Opti 175 - 431 lbs
Evinrude ETEC G2 175 - 535 lbs
New Merc V6 4stroke (lightest model avail) - 475 lbs
Merc Verado 175 - 510 lbs.
Yamaha F175 - 487 lbs
Suzuki DF175 - 522 lbs.
IDK where you are getting your information, but you are dead wrong. All those number came right from the manufacturers websites. Anyone who understands the differences between the two types of engines and has actually tore into them, knows that all things being equal (metal types, metal thickness, engine size, etc.) there is no way a 4 stroke can be as light as a 2 stroke. It's just physics. You can't add a head, valve train, cam shaft, and all the other parts that are needed for a 4 stroke and come away lighter than a metal plate with threaded spark plug hole and a carbon fiber reed valve of a 2 stroke.
The only way these 4 strokes get close to the weight of a 2 stroke, is going to be advancements in metal engineering allowing for thinner metal and different types/alloys to be used which equal less weight. If you in turn would apply those same technologies to a 2 stroke, it will be considerably lighter. The reason is, there is no R&D being done on the 2 stroke side (aside form evinrude) because our lovely government frowns upon mixing oil and fire.
And as far as Merc Optis having systemic issues... They had issues with the 3.0L block back in the early 2000s when they first came out, that was fixed in a few years. From what I've read, by the mid to late 2000s, they were pretty much worked out. The 2.5L block motors were always pretty reliable. Theres a reason that motor has remained relatively unchanged for roughly 20 years.
Go look at the bass boat market and show me how many 4 strokes you find. A lot of the used market is still running/rebuilding on Merc 2 stroke EFI motors because of the power they put out. The only reason Merc had to move away from the EFI motors to the Optimax motors was because of government emission regulations.
Bottom of the line, if you have ever been in the used boat market and did any amount of research on a particular outboard model, you will find issues here or there. But you are correct that as a whole, now a days, they are all pretty damn reliable compared to the motors of yester-year.
