Re: Towing Rinker 250 W/F-150??
Ford P/U and SUV have 2 tow tow packages:
Standard Duty and the H/D (heavy duty).
Easy way to tell which: The H/D package comes with the hitch installed at the factory with BOTH the 4 and 7 pin connectors installed on a welded-on-the-hitch bracket.
The standard duty has only a 4 pin connector.
Next item. You state 8700# towing capacity. Read the manual again, this ratin may be for an equalizer hitch, and could be derated to 5000# without the eq hitch.
I am towing a boat/trailer combo which weighed out at just under 8K (truck scale) with an '03 Expedition 4X4 H/D package) with the 5.4, 3.73 limited slip axle, yada, yada. I do use an equalizer hitch. I also have 4 wheel disks and a tortion bar suspension on the trailer, so it stops very well.
The towing is so smooth you can almost forget the boat is behind you. However, a professional trailer shop set it up to my specs for tongue weight (475#) using a scale.
If you do the above things I did, I will say your F150 will tow that rig OK.
With an aluminum trailer, allow about 1000#. So now you are at about 7300 dry. Add gas, and other stuff in the boat, I would guess at about 8500 towing weight, just within the limit.
Have the boat and trailer weighed at a truck stop weigh station. Their scales are certified.