this is the script I think it should work fine
local char = script.Parent
local healthGui = char.Head.HealthGui
local humanoid = char.Humanoid
humanoid:GetPropertyChangedSignal("Health"):Connect(function()
local healthChange = humanoid.Health/humanoid.MaxHealth
local healthColor = Color3.fromRGB(255,0,0):Lerp(Color3.fromRGB(60,255,0),healthChange)
healthGui.Health.Meter:TweenSize(UDim2.new(healthChange,0,1,0),"In","Linear",1)
healthGui.Health.Meter.BackgroundColor3 = healthColor
end)
everything is in place

5 comments
the code looks good, is
Lineaspelled the same way in your code, or is itLinear? b/c its suppose to be spelledLinearThis should work fine, I have tested your code, are you sure that you have tested on both the server and the client? Does it successfully show up or not?
i have tested but the health isnt changing
remeber its for a boat
The GUI shows up exept when i shoot it i see the humanoid health go down but not the gui health