Just bought a new Yamaha 90TLR-it's going on a 2070Mod-V Saturday. Friend is running the same unit - good lord are they awesome.
I'm partial- but if I was buying a new motor, it would be a "ricer" of one flavor or the other. Honda has a standard 5 year warranty, Yamaha a 3 year (but is offering 5 year now to move units toward season end)
If you want to know how your boat will perform - most of the Mfg's have links to performance bulletins on their site. You can search for a hull style/spec's similar to your's and it will give you the results of the Mfg's tests. For example, I couldn't find a bulletin on Yammy's site for an 2070 Mod-V, but did find one for an 1872. With a 13x19 prop, I know I can expect top end in the low to mid 40's, 13.5x17 more like Mid-Hi 30's.
Couldn't find a Yamaha bulletin for a 1648 - but here is one for a 16 Mod-V with a 70" beam - I'll bet you're darn close to these hull specs.
http://www.yamaha-motor.com/assets/prod ... f40tlr.pdf
Another rule of thumb - you should be running at least 75% of your rated horsepower.
The down side to being better than everyone else is that people tend to assume you're pretentious.