I can't add to this discussion, but want to say what I've done in the past when I've purchased a new RT.
My recent purchase was a new 2018 RT-27/OB (Northwest Edition).
When this boat was delivered to me at my marina it was lifted to the water. The lift had a scale meter so it was possible to know the weight of the boat as delivered.
The boat had around 60 gallons of gasoline fuel, and maybe 20 gallons of fresh water and an empty holding tank. The boat also had the F300 and kicker 9.9 HP engine installed.
The RT's "Dry Weight" specs for the R-27/OB is stated as 7,000 lbs. I'm unsure if the engine weights are included in this 7,000 lbs.
The combined engine weights would be around 600 lbs at the most.
The 60 gallons of fuel would be 6.3 x 60 = 378 lbs
The 20 gallons of fresh water would be 8.34 x 20 = 167 lbs
A new RT boat comes with a full set of fenders, lines, boat hook, a bag of manual and a bunch of life jackets. I estimate this to be around 100 lbs.
Thus summing the above items the extra weight is around 600+378+167+100 or some 1,245 lbs.
Adding the 7,000 and 1,245 we get to 8,245 lbs.
Guess what the lift scale displayed for my new R-27/OB when it was lifted up off its trailer ? It was 8,300 lbs. 🙂 😱 😎