496 Mag Exhaust Manifolds, Performance?

[phebus]

I tested the K&N head to head against the stock arrestor one day at Havasu. I would run one filter on a windward and downwind run, and then switch to the other. I repeated theese tests about three different times to get a true comparison. All speeds were taken with a GPS, and only wot top speeds were noted. After the tests, the stock flame arrestor edged out the K&N by an average of less than 1mph (.6 to be exact). the difference was so small, that I left the K&N on for the added filtering.

[Sweet Addiction]

Congrats on getting your new exhaust installed,I hope you get all the gains expected.
Now let me ask you this?If you were only spinning 4600 rpm before and now getting 4800 rpm,Why would you want to get your prop worked to get you back down to 4700 rpm.
If i'm understanding this correctly you are defeating the whole purpose of installing new exhaust system. Why not install the correct prop to get you up around 5000 rpm-5200rpm?A prop that gets you into this range is going to
be most effient.Not to mention will also feel like you just added some more upgrades. Like i said,i'm just curious here maybe i'm not understanding.
From what the Mercruiser specs says, a 496 Mag should run WOT at 4700 RPM, I thought adding just a hair to bring the RPM down would give me a little more push I.E. speed, and bring the RPM down in the correct operating range. Although I did run it a good hour, running at 4800 RPM flying through some waves and stuff and it never bumped the rev limiter. So, now I am really kind of scratching my head not sure which way to go. Maybe its at it peak potential just like it is? But I can't resist trying to push it over the edge so I can see 65 on that GPS.

[THOR]

From what the Mercruiser specs says, a 496 Mag should run WOT at 4700 RPM, I thought adding just a hair to bring the RPM down would give me a little more push I.E. speed, and bring the RPM down in the correct operating range. Although I did run it a good hour, running at 4800 RPM flying through some waves and stuff and it never bumped the rev limiter. So, now I am really kind of scratching my head not sure which way to go. Maybe its at it peak potential just like it is? But I can't resist trying to push it over the edge so I can see 65 on that GPS.
Damn!
There is no way I would have the balls to run my engine at WOT for an hour. Or even 5 minutes for that matter.

[Beer-30]

Damn!
There is no way I would have the balls to run my engine at WOT for an hour. Or even 5 minutes for that matter.
Why not? You think it's gonna last forever? Technically, it should run just fine with the stick pinned every time it gets taken out. For years. Until it gets up there in hours and starts losing compression.
In all reality, though, there are very few times one would even be able to run WFO for any length of time.

[THOR]

Why not? You think it's gonna last forever? Technically, it should run just fine with the stick pinned every time it gets taken out. For years. Until it gets up there in hours and starts losing compression.
In all reality, though, there are very few times one would even be able to run WFO for any length of time.
Cuz I am a pussy. I know I could but I just dont trust the motor to hold up. Dont ask why, I just am not a believer.

[Beer-30]

Cuz I am a pussy. I know I could but I just dont trust the motor to hold up. Dont ask why, I just am not a believer.
Hey, good enough. I just figure, if it lets go, the wife will want to still be boating. That will give me the green light to "get it fixed". They don't seem to understand that just because it is still running doesn't mean that it is running PROPERLY. :rollside: :rollside:

[shadow]

From what the Mercruiser specs says, a 496 Mag should run WOT at 4700 RPM, I thought adding just a hair to bring the RPM down would give me a little more push I.E. speed, and bring the RPM down in the correct operating range. Although I did run it a good hour, running at 4800 RPM flying through some waves and stuff and it never bumped the rev limiter. So, now I am really kind of scratching my head not sure which way to go. Maybe its at it peak potential just like it is? But I can't resist trying to push it over the edge so I can see 65 on that GPS.
Well i'm certainly no Merc expert but i'd be pressing to find out where your rev limiter is set.If you've run it up to 4800 and haven't found it then i'd look somewhere in the 5100rpm range.Someone also said recently that Merc says the impeller is good for 300hrs.At 300 hrs you'd be lucky to have any impeller housing left cause they wear so bad.My point is if you can run it up to 5100 rpm then run it or run it up to 5000 rpm.Find the limiter,do the math if you are at 4800 rpm and @ 63.5 now and you either prop or lab the one you've got so you can get all your rpms you should have no problem running at the 65mph that you'd like.Don't worry about over reving the engine thats what the rev limiter is there for. Good luck & like i said before i sure aint no Merc expert just my opinon and what i've found from personal experiences.

[Beer-30]

Well i'm certainly no Merc expert but i'd be pressing to find out where your rev limiter is set.If you've run it up to 4800 and haven't found it then i'd look somewhere in the 5100rpm range.Someone also said recently that Merc says the impeller is good for 300hrs.At 300 hrs you'd be lucky to have any impeller housing left cause they wear so bad.My point is if you can run it up to 5100 rpm then run it or run it up to 5000 rpm.Find the limiter,do the math if you are at 4800 rpm and @ 63.5 now and you either prop or lab the one you've got so you can get all your rpms you should have no problem running at the 65mph that you'd like.Don't worry about over reving the engine thats what the rev limiter is there for. Good luck & like i said before i sure aint no Merc expert just my opinon and what i've found from personal experiences.
Yeah, what he said.
I still say, borrow or rent a 22P B-1, and hit the limiter. Then, grab a 23P Quad-4 or other 4-blade that comes in 23P and check it out. Then on to 24s.
I would have to say you are close. Whoever is doing your prop work should have a smaller prop to start with. If you are just a few hundy away from it with your existing prop, just tell them you want another cupla hunerd and let her fly.
Like Shadow said, and he knows, don't be shy of the limiter. It needs to be checked from time to time. I should talk, I still haven't quite hit mine yet. But, I only have a couple of hours running the 22P. The few times I've stretched it out, I have been real close. Right around 5080, 5100 by my tach. My 24P only gets me to 48fitty or 4900.

[Pro Max]

I bought the eddie Marine Thunder Exhaust,,,,,,, Stay Tuned for the results
PRE EXHAUST 67mph 24p prop 5100 rpm
AFTER EXHAUST ?????? 26 LAB prop ??????
Maybee 70 or better ??? One can only hope and pray

[Beer-30]

I bought the eddie Marine Thunder Exhaust,,,,,,, Stay Tuned for the results
PRE EXHAUST 67mph 24p prop 5100 rpm
AFTER EXHAUST ?????? 26 LAB prop ??????
Maybee 70 or better ??? One can only hope and pray
That sounds reasonable. I would say you will get every bit of that.
You will definitely be above that 24P for this altitude. Like you said, a labbed 26 customed to about 25 will probably be right-on. I would hang on to the 24, though. If you went to Powell or higher, you would want it back.