I have an idea but it will take some modification to the trailer. The idea by-the-way is not original – I bought a boat and trailer with this feature and plan to modify the trailer I have now.
The tongue of the trailer was two concentric square tubes. There was a pin that held the inner in the outer. Pull the pin, extend the tongue and replace the pin. The tongue is now much longer allowing you to keep the wheels of the truck on solid ground while the aft of the boat was in the water.
I would lower the jack with the trailer still attached to my Ranger. Pull the pin. Then push the boat back till the holes lined up in the extended position and reinsert the pin. Raise the jack, and back it in.
Pictures below.