"BTW, the F70 and F90 are exactly the same in terms of weight, dimensions, etc. Only difference, I believe, are the stickers and ECU...and the price"
Not true, the 70 is 1000cc and the 90 is 1800cc, the 90 is much heavier, 100# more. The 70 is only available in a 20" shaft and the 90 comes in 20 or 25". The 70 is basically a motorcycle engine with great HP/weight ratio. It was designed for the 16 to 18' technical skiff market.
https://yamahaoutboards.com/en-us/ho...15-50-hp/70-50
https://yamahaoutboards.com/en-us/ho...115-50-hp/f115