I was doing some online research and came across this article on Marine Exhaust Reversion.

http://www.michel-christen.com/ExhaustElbows.pdf

This might be of use for someone looking for a basic first time explanation or even us old dogs that need a refresher from time to time. LOL

good info sprink58,thanks for posting it.

Good read. I saved that one... I had reversion on a 496 exhaust and a 2" taller riser solved my problem...... I am using a larger than stock cam and 10.2-1 CR so I guess I was in uncharted territory....... I would say that there are definately a few variables that affect how and if you get reversion.....

You know...the BIG issue this reminded of was the reversion.and resonance reversion that causes" the exhaust water returning back towards the engine instead of discharging out the tailpipe." It's likely to experience this while the engine is just idling with the boat sitting still !! I checked the very latest wet and dry joint Mercruiser Exhaust manifolds when setting up the engines in my boat ...to make sure I selected the design that minimizes this phenomenon. Be mindful of the differences in exhaust manifolds when you consider replacements or for new installs. If you make the wrong choice...you can easily and quickly destroy all of the good work you have done developing your power plant !!

I have also wondered how much of a factor exhaust port design plays into this. It would follow reason that if your port flows better in one direction, it will also flow better in the reverse direction.

This is true.

Great find Gonna save that one for sure Thanks

Good read. Thx Sprink58! Makes me wonder what a cut-away of my IMCO Powerflows would reveal.

The "Revolution Marine" manifolds that were made had this "break" cast into them and still had good flow performance for a more radical cam use. That is what was on my stroker engines in the 357 I sold. To bad revolution marine got bought out. I believe it was Eddy Marine that bought them and I wonder if their subsequent product is properly made?
Good read and interesting evolution of loosing focus in the marine world of production for the almighty dollar instead of quality product well researched and produced. People in a job capacity they can't perform is very wide spread these days; terrible.



P.S. incidentally those who are attentive to their work in a knowledgeable service can read the plugs when they are removed to get early detection of reversion and help protect the customers engines. If the "mist" is happening the plugs will also show this loss of carbon as a "tip of the iceberg" indicator to look further or test or repair for a solution to bigger failures like valve failure or hydro-lock.

Gentlemen...this Reversion issue is Serious ! Truth be known..it wouldn't surprise me that a great percentage of engine damage in Performance Boats is due to this very issue. The "Beak" that Aquaforce refers to is nothing more than a simple casting mold addition to keep the reverse flow of water to a minimum.

I'm surprised more exhaust manifold manufacturers don't include this feature and aggressively market it.