Mercury 115hp power trim question

[stovepipe66]

I have a pair of 1990 Mercury 115hp O/B and my power trims are bad. What happened to them is this I was on a lake and did a no brainer, I went into too shallow of water and both outboards hit and popped up. My props and bottom of my skag were damaged, I have since fixed the props. The problem I have now is my power trims do not stay up they seep down and i can grab my leg and pull up my outboard with little or no resistance, same happens when I'm on the water and traveling down the lake when I let off the throttles the engines come up from the water pressure. I've tried overhauling them with tilt trim kits, though I haven't put new o-rings in the pump assembly. This hasn't helped. My question to you experts is I want to change out the entire units but having a hard time finding some. There is a guy on E-Bay that has two units but there from a 1997 225 EFI Merc. The unit looks the same other than the filler tube and it's a two wire system whereas mine is thre wires. Mine has a filler tube this one does not, the pic is the one for sale. Would this work on my 115's or am I **** out of luck? Also how do you convert a two wire power trim to a three wire power trim.
Thanks for any response
Steve