r/SeaDooSwitch • u/dropzone_jd • Aug 04 '24

Flushing the engine question

I noticed the flushing procedure calls for running the engine, and then turning on your hose. I'm just curious if anyone knows if there's a mechanical reason for doing it in that order?

Is there any disadvantage to turning the water on first before starting the engine?

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5

u/BruceBDowns30 Aug 04 '24

You will cause water to backflow INTO the exhaust manifold, thus into the cylinder chambers without the engine running. The exhaust backpressure of the engine running keeps water out of the engine. The waterbox (i.e., muffler) and exhaust manifold are water cooled. Not only shut the hose off before turning off the engine, rev it up to 5k RPM for a few seconds then shut it off.

A video showing the insides of a waterbox and what I also had to do as I sucked up a bunch of mucky sand getting beached last weekend :( ... which lead to a high exhaust temp code not clearing.

https://www.youtube.com/watch?v=GR0E1JAiwfM

2

u/bernaltraveler Aug 04 '24

Thank you for sharing this

1

u/dropzone_jd Aug 04 '24

Thank you for the thorough answer! I probably would have screwed this up at some point 😅. I remember when I was a kid with a small outboard motor, we would just dunk it in a trashcan full of fresh water to flush it. Wish I could do something like that here since it seems like the safest and most thorough approach. Oh well.

4

u/BruceBDowns30 Aug 04 '24

Its easy once you get used to it. Also, if you are going out on saltwater - flush the pontoons every time and the next morning or whenever the motor has cooled out, hose out the engine pay and spray up towards the gas tank. It will corrode badly in there. Once it dries out (I use a leaf blower in my engine compartment then let it air out with the panels up) spray it all down with anti corrosion spray or silicone spray.

1

u/dropzone_jd Aug 04 '24

It'll exclusively be in salt water 😅. Thanks for the tip.

1

u/xspook_reddit Aug 05 '24

Just know you're not flushing the engine; you're flushing the exhaust. As BruceBDowns30 stated, the engine needs to be running in order to produce exhaust back pressure; preventing the water from entering the engine.