I have a 175 Verado Big Tiller. Over 1200 hours. Granted I have had a Couple of Issues ie: Fuel float (Ethanol issue) and wiring harness (Hundreds of hours of back trolling). Overall No oil issues, No lower unit issues, No blown power heads, Great performance and Great trolling. I do all the maitenance myself; oil, fuel, lower unit done on suggested time frames. Can’t say enough about the big tiller I only use regular Starting/deep cycle batteries never any problems. For me Four Stroke all the way.
You may want to look into the new 150 Four Stroke. Looks like a pretty awesome motor. Sounds like they built it like a tank and not much heavier than an Opti.
I have a 2008 and Merc has always covered repairs under warranty and Lybacks Marine has done those repairs. They have been great at getting me back on the water quick.
JT