Finally got someone at Trail King to get me an answer. They recommended 15gpm at 3000psi. Most of that I knew but the big answer I keep looking for is 12 gallon reservoir. Figured I would post the answer for others. Thanks for the input guys.
I know they make one with an onan motor and one with a Honda and onan is a lot better ! But I think it’s about $800 more
On our first truck and trailer (Ford LNT9000, Trailking hydraulic beavertail) we built our own pony hydraulic unit. Used a 30 or so gallon tank, honda GX160 motor, and a hydraulic pump we had from some obsolete equipment. I sold it since, the pictures are here: Hydraulic unit Honda GX160 gas motor vickers PVB5 RSY 20 C 11 pump 17217 The good news is that worked. The bad news is that it had some sticky points. Number one is that it was hard to start in cold weather. Believe it or not, our solution was to cover it with tarp and run a exhaust hose from the truck exhaust under the tarp to warm it evenly. It worked well but was ridiculous. What I know is that pressure matters, but the flow does not really matter. Pressure is force, and flow is speed. So, more flow, faster movements and less flow., slower movements. I agree that a wet kit is the way to go. Much more reliable than a pony motor. And more power.
Most trailers run on 2500 psi, which is pretty standard in the industry. The gpm just depends on how fast you want the trailer to operate. Around 12 gpm will be plenty fast enough. For what it's worth, I despise pony motors. Just another engine to upkeep and it seems like you run out of gas at the worst time, and another battery to have to deal with.
We chose a pony motor because of our operation structure. Lowboy is a fraction of our work. Our trucks pull tank trailers most of the time. Those require a different PTO set up. By running a pony motor we can still put any truck on the lowboy. Every operation has something to consider in how they set up.
We had already decided to use stabil in the gas all the time. My opinion this should be looked at in all small engines because of ethanol in the fuel. That stuff will eat small carbs up. We also run it out of fuel with the shut off valve when parking it. Good advice for any small engine.
I totally agree on shutting off the gas and running out of gas in the carb, it solves 99% of problems.