Originally Posted by Kanookstr

Unfortunately they were not designed for water reversion. They are designed to trap any condensation that might occur after engine shut down. By trapping this condensation it prevents any chances that the condensation can reach the iron valve seats/guides. this problem is seen more in the northern states where the water is much colder. It is more of a problem for people who keep there boats in the water. A proper idle down time before stopping the engine will help reduce the chance of this condensation from happening, They will do nothing to stop or prevent reversion. The fact that they reduce the exhaust hole from 3 1/4 down to 2 1/4 is a definite restriction.

I plan on cutting mine down to maybe 3" so to have some protection , but better flow.
If you are worried about the problem by removing them, then going to an after market exhaust will still give you the same condensation problem, because the after market exhaust don't have the tubulater design neither.

The picture is also deceiving because the cut is not thru the center. So you can't really see the 1" difference in hole size.

Originally Posted by Chris288

I took mine out and wasn't completely happy w/ the results,,, the motor was pulled to replace the transom assembly and gimble, the dealer doing the work re-installed them, i'm gonna see how she runs before I decide if i'm gonna take them out again.. I honestly dont think there are any measureable gains I know some people have seen 2-3 mph, I couldn't even be sure I saw 1 mph..

Originally Posted by Strip Poker 388

I was told by people that sell the CMI's for the 496's you may not see a increase.



They do look restrictive

Originally Posted by fbh-velocity

The reason why the restrictor plate are build in is to prevent water reversion. Under run it gets really hot caused to the thin sheet metal and non cooling area and will catch the water and steam it out. Just an insurance from factory

Originally Posted by PENN YAN

I have been reading up on 496 MAG posts after newly joining this forum. I will be pulling risers to inspect this spring and was boning up on the manifold design. Those cut outs are a great view! There are good articles on Perfpro tech and hardin marine about turbulators. The bluf is they are to accelerate exhaust flow up and out (along with any moisture buildup) and trap moisture buildup which may occur during the cooling process. They will provide exhaust backpressure and pressure drop but in the end I would not hesitate to risk changing the design to get a few more hp and will be spending the money to re-install them as designed.