How much force is on the top cover on the drive shaft housing
 

the top cover on my drive shaft housing is held by four screws. It is an alpha I gen 2. One of my screws sheared off. Does anyone see any problem running with just three screws? I tried to get my top cover off but it is corroded shut. I was trying to get a screw off to install a drive shower and the screw snapped due to corrosion.

If the cover were to loosen up would the drive blow or just leak?

Thanks

ouch, its a risk. if it loosened up, both.

The upper gear case cover is critical to the proper alignment and preload applied to the upper drive gears. I wouldn't think of running the boat without that cover bolted down correctly. Aftermarket companies like Teague, make billet upper gear case covers to help prevent even the smallest amount of flex that the stock Merc. cover allows under extreme loads. I can't imagine that running the boat without it bolted down can cause anything but a disaster.

FlyFast, I would pull it off and fix the problem. If you don't, you are just asking for problems. You really should have the drive shower anyway, so you will need the screw to hold it. That Alpha will produce as much or more heat than the bravos. If it loosens up, and it will, it will blow. You probably didn't want to hear this, but fix it now while in the off season. Avoid the hassle and cost, not to mention leaving you stranded at the worst time. Good luck!