lower drive
 

I have Twin 1997 Bravo 1 with lower water pick ups. 337hrs. Just did motor upgrades to 540ci 650hp. 32 ft boat deep v . Is the lower drive the weakest link? Any thoughts would be apreciated.

Your uppers will be the weak link. Technically you are over the rating of the XR's but IMO you could replace the uppers with XR's and keep/use your stock lowers. (that's what I would do, and a buddy of mine just built the same motors and is doing just that)

I just did the same thing with my boat. I am going to the -2" shorties from Imco and leaving the uppers stock. Was going to do the uppers, but thought I would take a chance when I priced out the upgrade.

lower drive
 

Imco shorties and the same props? Or do you need to change
I was told to leave the stock Bravo uppers and replace the lowers with Imco shorties? I just want to do whats best to make it through the summer. Then next winter a complete face lift and drive exchange.

The nose on the imco is going to give your props more bite (less slip). If you want to save the drive I would keep the stock lower.

My buddy was running 860 hp on stock bravos and never blew a lower...the uppers on the other hand......

Dean there are a lot of factors that go into this equation. The standard Bravo 1 has many weak points. Depending on how your boat is driven, and what type of water you run in, will be a big factor in drive survival. The upper gears have weak floors in them, the shafts are weak and with 337hrs, lower gears may be worn to a point of causing a problem.
I have witnessed Bravo 1's surviving large amounts of power, but in each case it is due to the way the boat is driven.. If you tape and egg to the throttle, then you may be ok.
Torque and load is what breaks them. Too big a prop, too much throttle while the hull is still too wet, etc. If the drive is loose, which it can be with 300+hrs, that can help the self distruct mechisim.
Rebel Heart and I just worked through this same senario, as he said. His decision was based on how he boats and how careful he will be till he can upgrade the package. If you like, call me and I can help explain what might or might not be a good route to take. In the end, it will only be the right choice, if it survives the summer. If not, then the other choice may have been better! You have enough power to break parts. The goal is not to. So any route you take, other than building the strongest drive possible, could be the wrong choice.
Give me a call and I share what I have experienced..

D*ck
616-335-8446