M-Y-T-H!

Here's our Tsikoteer mythbuster at work:



AFAIK - more than 5 hours naka idle lang ang engine while the exhaust is submerged in water.

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To note also, in order to maintain that "high rpm level", you need to use your clutch.

And using your clutch when crossing floods / water should be avoided as much as possible!!!

The engine at idle already has enough pressure to keep water out of the exhaust.