Unfortuanatly the strait answer is no, there are no rebuild kits and no new units that fit. The cheapest replacement that would come close was in excess of $800. and then it would need to be modified to fit. That being said there is light at the end of the tunnel. I rebuilt my hydro for a 3700 myself using parts obtained locally from a bearing store. Somewhere in these posts there are pictures of the rebuild. If you look for YT3700 hydro or something like that. My unit was abused by the previous owner and the oil was never changed, bearings burned up and spacers were scored. I carefully dismatled the unit, took the old bearings, what was left of them, to the store and the counter person was able to measure them, and order replacements. Not the perfect fit but with some shims we were able to come up with the proper fit and clearance. I had to polish some of the internal mating surfaces with 600 grit wet/dry paper but they came to a mirror finish that was needed. It's been running strong for over a year now without any problems.
A lesson to be learned to keep the hydro oil clean and fresh.
No rebuild kits per say all parts are sold individually, if you view the pictures I have included, you can email me and I will respond with price and availabilty to your location.
Speedy
Picture # 1
I am trying to rebuild my hydro, saw in your post you had done it. In disassembly, one of the three steel ball valves came out of the unit, and I never saw where it came from. I know where 2 of them go but the third, has me baffled. Do you remember, know, or have a drawing of the hydro valve body and whats behind each plug? Thanks
Sorry for the long delay, just got back from vacation.
It's been a long time since I did the rebuild and my memory is foggy. I replaced the needle bearing assembly and had to add some spacers because the exact bearings were no longer available. The ball valves I more foggy on. If you can send a picture or two it would make things easier meanwhile I'll see if I can dig up my old files.
The straight factory oil is 10W30 motor oil, but after a rebuild, a good synthetic or heavier oil probably would be better. If you look back at Meofuse's posts on changing/rebuilding the hydro, there's some info there.