First, like someone stated above, your stomach pH won't be very much affected by the alkalinity. Basically, your stomach pH is very low, pH 2 is normal. Since pH is a log scale, you would need to make it ten times less acidic to get a pH of 3. Som slightly alkaline water solution won't get it there, especially since the stomach fluid is a buffer which helps maintain a constant pH. Dilution will help more, depending on the volume of stomach fluid. However, your stomach will produce more acid to make up for it.

Second, now you still have to get the pH of the whole body higher, which means raising the pH of the blood. The pH of blood is about 7,4 and it is also a buffer. You have 5 liters of blood, which get constantly pumped around the body. If there were something jacking the pH of your blood (via IV), your kidneys would remove the alkalinity again, right up to the point of kidney failure. This is where you die.