Quick search .. Yamaha 90 HP motors were made from 1985 until 2009.
Might have been built longer ..
The 90 HP was bigger (cubic inch/CC) then the 70 HP motor.
Around here (Minnesota) the 90 HP Yamaha motors go for top dollar, if you can find one.
A nice 70 HP Johnson / Evinrude would be much easier to find .. and cheaper.
Some member have brought boat/motor/trailer just for one part off the package, because the total package was cheaper then the single part they wanted, then sold the other parts. So if you found a good motor on a rotted hull for cheap, you could scrap the boat, sell the trailer and use the motor .. Or put your old motor on it and resell it.
V156 / 60 HP Johnson