496 HO manifold restrictor plate removal?
 

In past threads Raylar has mentioned that the 496 has a restrictor plate between the manifold and riser which would free up 15-20 hp by simply removing it. Has anyone checked into this and actually removed it and if so, what's involved? This to me seems like a fairly simple task to let the 496 flow better and even sound better... What are the pros and cons? I'm bored waiting for spring and need something to do... :D

Re: 496 HO manifold restrictor plate removal?
 

Sounds too easy. Why would Merc put them in there if all it did was lower your HP? I thought I read somewhere on OSO that someone removed them with no positive results.

Re: 496 HO manifold restrictor plate removal?
 

i think it was just on the 01 496's after that year they dont have the restictor plate ,I have an 01 thinking about doing it in the next week or so,will let u know what i find out.

Re: 496 HO manifold restrictor plate removal?
 

My understanding is that they prevented reversion. Don't get me wrong, I'm not expecting a big performance increase by removing it. I'd just feel better knowing the restriction was gone and possibly free up 15-20 hp. And if it's simple to do then why not... :D

Re: 496 HO manifold restrictor plate removal?
 

If you get to it before I do, let me know what you find? I have a 2001 Daytona, so I don't know if the motors are 2000's or 2001's? Actually theres a sticker on the PCM 555 ecm that says 2002, which doesn't make any sense to me. Good luck

Re: 496 HO manifold restrictor plate removal?
 

will do, won't be able to run it for another couple of weeks,but i will let u know what i find when i take them off

Re: 496 HO manifold restrictor plate removal?
 

I don't know if you will notice any significant improvements by removing them. I did help a friend install a Whipple on his 2001 2 years ago and the instructions had us take them out. He has no problems because of removing them.

Re: 496 HO manifold restrictor plate removal?
 

Like I said before, I'm not looking for it to snap my head back once removed. I just want them gone and no restrictions. Since you have removed them before, what exactly do the plates look like?

Re: 496 HO manifold restrictor plate removal?
 

10 or 15 horse is about 1 or 1.5 mph depending on the hull

Re: 496 HO manifold restrictor plate removal?
 

Were talking 15-20 hp x 2, so maybe 2 mph in the Daytona. I'll take that in a heartbeat just for taking out some plates. Might even sound throatier too... :D

Re: 496 HO manifold restrictor plate removal?
 

Let Lori drive because it looks to me that they're going faster,I mean the boat is going faster. :D :D :D

Re: 496 HO manifold restrictor plate removal?
 

might get a little more bounce ;)

Re: 496 HO manifold restrictor plate removal?
 

The Restrictor Plates Are There For A Reason Reversion If They Wernt Needed They Probably Wouldnt Be There. For 1-2 Mph I Will Leave Mine Alone. Who Needs A Motor Full Of Water!

Re: 496 HO manifold restrictor plate removal?
 

they were only in the early model 496's the later models don't have them,i believe it was an extra security measure on a new motor.

Re: 496 HO manifold restrictor plate removal?
 

The restrictor plate that you mention is called a Turbulator and is made for Merc by Gil Exhaust Systems. It is supposed to keep condensation out of the exhaust valves when the motor cools. My 2002 Baja with 496 HO's has them in place. I have also considered removing them. If anyone can verify their absence in newer 496's please let us know.

Re: 496 HO manifold restrictor plate removal?
 

Last summer I installed a 2004 model year 496HO. It had the turbulators.

Dave

Re: 496 HO manifold restrictor plate removal?
 

Good points to consider, but sounds like they're not really necessary and safe to remove. I'll take all the free hp I can get, plus a little extra hp goes a long way in a cat... :D

Re: 496 HO manifold restrictor plate removal?
 

I will see if I can intelligently answer the questions and put a final light on the Mercury "Turbulator" plate in the 496 engines. First, all the 496's I have seen or checked seem to have the plate irregardless of year of manufacturer. Thats not to say Mercury has or will not change on certain production years and models. As I understand from Mercury engineers themselves, these plates wetre designed to catch small amounts of exhaust moisture, not reversion!, no plate will stop reversion, reversion is a function of cam timing and overlap and it does not exist per say in the 496 Mag or HO engines. Exhaust moisture, depending on the individual boat , exhaust design and exhaust system exit heights coupled with silent choice or otherwise can sometimes be a greater water generator issue in some hulls more than others. The plate was designed to provide a substantial shelf to catch small amounts of actual water and provide a place where exhaust heat could cook it off and keep it from entering the exhaust manifold and possibly getting to the exhaust valve, especially after the motor is shut off. The idea is not a bad one but the execution was not the best. first the inside diameter of this hole in the "turbulator is just over 2-1/4" inches in size. This does not seem like a serious dimension, however you need to understand that the inside diameter of the Mercury sweep riser is over 3" and about 3-1/2" at the location of the "turbulator" plate. This small opening becomes a substantial restriction to the exhaust gas flow at higher rpms, especially under full WOT periods. Remember this is a fairly high horsepower 500 cubic inch engine! We have done actual flow bench runs on the manifold and riser, with and without the turbulator plate and I can personaly tell you that removing the plate has a considerable affect on how much exhaust gas the manifold & riser plate can flow at what would be higher rpms and throttle positions. I wish the manifold designer-Gil? had just designed a little more down angle to the exhaust port entrance at the cylinder head flange and any need for the turbulator plate would have been completetly eliminated. The low pocket this would have created would cook off small amounts of water., but what the heck, I didn't design the manifold, and it's really not a half bad part. This manifold is every bit a good as a normal aftermarket cast manifold such as Stainless Marine, Gil, Eddie or Imco standard . If you have a boat that has a s-pipe drop tube between the riser na d the transom exit tip or your boat has a moderate drop between the riser exit height and the transom exit you should be able to eliminate the plate and get the horsepower benefits accordingly. If your transom exit height is close to the bottom of the Merc riser height, you have a silent choice system which you keep set closed for through the prop exit a lot or you are one of these boaters with a below the water line tip exit, swim platform cap over the tip and you back down hard a lot of the time, then you may be better off keeping the turbulator plates installed. If you can safefly remove them, especially with our BIGPOWER kit you will gain power at higher rpms. Remember any impediment to air flow into or out of a high performance large cubic inch engine, especially in marine use will have a negative affect on performance. Otherwise no one would need to purchase marine header or high performance marine manifold systems. I hope this clears the air and clarifies the issue. "Will the real Turbulator plate please stand up!"

Good Luck,
Ray @ Raylar

Re: 496 HO manifold restrictor plate removal?
 

That clears the air for me... :D thanks raylar

Re: 496 HO manifold restrictor plate removal?
 

Heres what i did with mine

Re: 496 HO manifold restrictor plate removal?
 

Have you ran the boat yet without them? Any difference in performance or sound?

Re: 496 HO manifold restrictor plate removal?
 

I removed the stock Formula exhaust panel on the back of my boat and put switchable exhaust tips.also I put prochargers on it so the performance I could only say is much better because of the boost but there deffinetly is a better sound.. ran it a full season so far.....83mph at 5100rpm

Re: 496 HO manifold restrictor plate removal?
 

Is it as easy as removing 4 bolts remove restrictor and tighten the bolts back up?? Or is there a gasket that needs to be replaced etc..?

Re: 496 HO manifold restrictor plate removal?
 

I wondered that too?

Re: 496 HO manifold restrictor plate removal?
 

There is a gasket on either side of the plate that you must replace - a total of four for the engine - I think they come in packs of four from Mercury when your order them - it is as simple as removing the four bolts and lifting off the riser - (after disconnecting whatever you're running on the other end for exhaust.) No need for torque on the bolts, I was told, just tighten.

Re: 496 HO manifold restrictor plate removal?
 

Is replacing the gaskets an absolute must after removing the turbulators? If so whats the Merc part number?

Re: 496 HO manifold restrictor plate removal?
 

Merc Part# 27-862356 $ 4.65 ea

Re: 496 HO manifold restrictor plate removal?
 

Yep. As I recall the gaskets are the same material on each side, so you remove two, would replace with one. I saw another thread on HotBoat.net on the subject and I think they said there that Whipple recommends the removal of the plates as well, when using their blower. Like Raylar, I'm sure they did a ton of dyno testing and possibly real-life testing on the 496 before making the recommendation. I think they also said there that it makes the engine louder (makes sense).

Re: 496 HO manifold restrictor plate removal?
 

Let me get this straight... I'll need 4 total for two motors? :D

Re: 496 HO manifold restrictor plate removal?
 

Maybe we should discuss has to unscrew the bolts before we get too far ahead of ourselves.

Re: 496 HO manifold restrictor plate removal?
 

Ok then, I'll order 4, but once I go in and find that I need more, some heads are gonna roll... :D

Re: 496 HO manifold restrictor plate removal?
 

I removed my restrictor plates last week after reading these threads and gained about 100-150 RPM and about 1.5MPH on the GPS. Exhaust sounds a little deeper too.

2001 Baja H2X with 496 Mag HO. Thanks for the advise on easy HP!

Re: 496 HO manifold restrictor plate removal?
 

Kewl....!

Re: 496 HO manifold restrictor plate removal?
 

:D: :D: :D:

What's the final story on these plates? Help or do more harm?

Ray is right. I did talked to Merc. about ths for my 496's.
In short. If the warranty is up.. remove it in the warmer/Southern states. Less condensation. Important to "warm" and "cool" at start and shut off to burn off any moisture. Merc. does not reccomend it officially, but will admit some little HP gain, with no negatives, but possible moisture issues.

I think that Bobl from Full Throttle Marine has had some experience in removing these and has tested the results. Maybe he will chime in here.
Jay

Bob LLoyd posted his dyno test results with and with out the turbulator on his Full Throttle Marine web site. Removal neted 8 hp. http://www.fullthrottlemarine.com/49...%20Article.htm.

Thanks - any hp numbers on the MAGS ?

How fast is your H2X running ?