Can I just say that when going to carb heat to check for icing, leave it that way for some time - twenty to thirty seconds is a good minimum time.
Think about it please - you are trying to melt any ice. That takes time and energy, so applying carb heat 'for a few seconds' is fairly pointless. Tells you nowt.
And if you have got icing, expect the engine to start running even more roughly as the ice melts. Engines tend not to enjoy gulping water. (No, this is not how water injection power increase works !)
So, when the engine sounds like it is going to die on you after pulling carb heat on, don't immediately go to back to cold power - keep carb heat on while turning towards a suitable field, just in case.
This affects any carburettor equipped aeroplane in the wrong circumstances.
Also, I recommend you don't wait till you start a water crossing before checking carb heat. Guess how I know!
biscuit