Boat damages more quickly when touching more amount of lava

Description: Boat damages more quickly when touching more amount of lava.

Steps to Reproduce:

1. Place lava on the floor
2. Place boats on top of the lava.
3. Place boats at the margin of the lava.

What you can see in step 2: Boat burns really quickly.

What you can see in step 3: Boat burns more slowly.

What it should be: The burning time should be the same.