It is a lot for 50 sq ft, but a lot depends on how well composted it was, the type of soil you have and how deep you till it in.
The nutrients in the manure will be released slowly and it should not burn if it is well composted, but there will be a lot of salt. How much of a problem will depend on how much salt you already have in the soil. If you have sandy soil it will leach quicker.
For me, that much compost in my clay soil and with rain would stay to wet and be more alkaline. for the already alkaline soils in a couple of gardens. Manure is heavy so if it has a high moisture content 80 lbs might not be that bad. I usually put about an inch on the top of the soil and work it into 6-8 inches of soil when I do use it. pH of steer manure tends to lean toward neutral but composting tends to make it a little higher.
Happy gardening in Hawaii. Gardens are where people grow.