1. Is the powertrain warranty really voided if a dealer doesn't perform the 25 hour service?
No.
2. What did you pay for the 25 hour service? Seems like replacing the serpentine belt that early is a touch overkill?
My boat had 26 hours when I bought it (was used at Regionals) and they did the service before I picked it up.
3. Is the heater really electric, versus the Heatercraft style running off the engine cooling system? My boat is being stored at the dealership, otherwise I'd pop the hood and look for myself.
No, it runs off the engine like every other boat I had, though it does not put out nearly enough heat.
4. Are fold down platform brackets standard? Mine has them, but just curious if I paid extra, as they're not listed on the build sheet?
Not sure, but I think so.
5. Is it hard to add seat heaters?
Yes, I was told it can be done, but expensive.
6. Mine is has a 4 blade prop. Since a 3 blade is standard, what package was the 4 blade a part of? Seems like a dumb question, but my dealer doesn't have an answer for me. I'm assuming I'll prefer the 4 blade? 5.7 engine, if that matters.
Every 2014 through 2016 I've seen here in South Florida came with a 4 blade.