Affraid of reversion, exhaust HELP?
 

Bbc 509cid, 9.7 comp, roller cam,230/236 @050", 112lsa. Dry section of the riser is now approx 15" longer than in normal riser, 6" taller + 9"longer. Is It possible to use the silent choice diverters? I could limit the water flow going thru the exhaust if needed. The line attached to inner transom assembly shows the transom line.
https://cimg0.ibsrv.net/gimg/www.off...c5d218bb38.jpg

https://cimg9.ibsrv.net/gimg/www.off...b1aa30ee6f.jpg
Considering to buy extender bung for the h2o sensor.

You could run any regular performance exhaust with diverters with that cam. You basically have a 500efi cam or similar.

Ok, so I could leave the diverters like they are and not modify those to reverse type diverter, and still be ok?

500efis are known for small amounts of reversion at idle effecting the back two cylinders.

Atleast my engines showed signs of it when the top ends were rebuilt.

With silent choice?

Merc 500 efi cam, 230/236, 114lsa. 5° overlap @050". My cam, Same duration but 112lsa, 9° overlap @050".

how would you guys reduce the water flow out of the riser? how big holes would be enough to keep things cool? i know this is been done thousand times but cannot find any threads about this subject. my cam has almost twice the overlap @ 050" compared that 500efi cam, dont want damage a fresh build engine.

Just a thought- take the risers to a skilled tig welder and have him extend the inner 3" pipe through the transom. That's what I did when I got tired of worrying about reversion.

This is what we did when we were concerned…run dry exhaust.


https://cimg5.ibsrv.net/gimg/www.off...c2b8daf4d.jpeg

Offcourse, but the silent choice is a must for me.

My ears hurt just for looking the picture :D. And yes, i love the big inch bbc sound but not in every situation.

I totally agree with this^^^ it works, you should give it a try.

Allready extended to the transom, check the pictures of the first post. I have a pair of CMI sound eliminators, but dont know how much those will effect, not much info about them in the internet.

https://cimg8.ibsrv.net/gimg/www.off...2ed0341e40.jpg

I used to run CMI sound eliminators, they work well and are convenient as they are automatic.
However they don't work well for engines over 700 HP as they can't flow enough exhaust gas.

The extended risers you show with the silent choice you have pictured makes no sense. How could that possibly work??

Thats true. the diverter is just laying on the inner pipe extension , wich is not cutted yet, but it is impossible to know the correct extension lenght before the engine is installed to the boat. Trying to get the diverters as near as possible to the transom, so the diverter outlets for the y-pipe is going to be cutted of and turned 180deg, that is not yet done in the picture, but i tought it would give an idea how it looks like when it is done. the riser dimensions in the first post are rough estimates of the final dimensions when everything is fitted. Hope this makes sense.

Isnt the diverter location dictated by the y pipe location?