He Fired When Ready-- Part 6: The Losses at the Battle of Manila Bay

The Asiatic Squadron had suffered few casualties.  Only six wounded.  However, on the Spanish side, nearly 400 sailors died and ten warships either destroyed or captured according to The History Channel site.

This source says that after two hours of the fight, the Spanish fleet was so decimated that Dewey met with his captains and ordered his crews to have a second breakfast.

Wikipedia says that American losses were 

1 dead of illness

9 wounded

1 protected cruiser damaged

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Spanish losses were

77 killed

271 wounded

2 protected cruisers scuttled

5 unprotected cruisers sunk

1 transport ship sunk

Anyway you want to look at it, this was one big disaster of a battle for Spain.

Like I Said, It Was Very One-Sided.  --Cooter