OMC SeaDrive 2.0L Won't Start

[bgares]

Ok...finally had some time to put in to the boat this weekend (been a crazy few weeks at that place that pays the bills). I finished rebuilding the one carb that was leaking, cleaned the others out. Did a Link & Sync (to the best I could figure out). Put a new in-line fuel filter in, as I had no idea when the other one was from. Finally, it was time for another test fire. She continued doing the same it did before (would fire, 'burp'/backfire, then stall out). I decided to try to start with the throttle open a bit - started about 10% throttle, and worked my way up to about 50%, and it fired up! I immediately backed down to neutral after it fired, and it stalled right out. No matter what I did, unless the throttle was opened up a bit, it wouldn't stay running. After 2 tries like this, I decided to call it quits on starting until I could get back here and get some more advice. After getting out of the boat, I noticed a little smoke/steam coming from the exhaust ports. So, I guess I need to replace the water pump (planned on doing this anyway, just haven't been able to figure out how to yet). I also drained the gear oil, and plan on replacing that too. So, my newest questions:
1. How do I get the lower unit off to replace/rebuild the water pump? I found the 6 or 7 bolts at the bottom, but after taking them off, something is still holding it.
2. Any advice on why it would run with the throttle open, but not at idle?
3. What's the best oil to use to refill the gear case, as I doubt the OMC Hi-Vis Gear Oil recommended by the manufacturer is still available!

As always, thanks for any insight/help. It's greatly appreciated! Here's to still hoping I can get my grandpop out on the boat one more time!