Pete at Smoothwatersports has been selling this jack with a homemade plate so you can bolt it up to a Boatmate trailer. I purchased one a month or so ago and did the install today. It took about 30 minutes, start to finish.
When removing the original jack, you've gotta trim the stud so the plate fits flat. After that, it's completely bolt-on. All hardware was included and it was all straight forward. The new jack is a lot more sturdy. Cranking seems to be the same but I only turned it about 3 turns.