I just installed a new XR drive and am currently running about 625 HP . I am looking to redo the motor this winter a was wondering what HP I could run threw the drive within reason.

Looking at your avatar photo I would say you are at the limit now. 700 maby in a 5,000 lb boat

if you keep it in the water and not slam it it supposed to take it but its all relative to driving habits. if your going to operate it anything like the pic in avator youll be fixing it a lot

Merc rates them for 600 HP. If you are kind to them, you can run more through them. Sooner or later you will toast it, though.

Ran my XR with a merc 600sci for 3 years and 280 hours, no problem, after 3 hours with the 800 efi broke the upper. New upper and rebuilt lower and 10 hours later no problems, come on plane slow, try not to get air, and short wot bursts you should be ok.