what is the best exaust? thru or prop?

[oops!]

19 footer, 350-383 (either one) i/o

will i get more power with thru hull?
ive heard that a stock setup is very good at letting the motor exhale.

whats the truth?

thanks
oops?

p.s. mods.
i thought i posted this quest earlier but cant find it. so if this is a double post please forgive me

 

[MikDee]

Re: what is the best exaust? thru or prop?

IMO thru-hull is better, from my "butt dyno", of course I can't verify this,,, but, I'd say your engine runs cooler, that usually means more power, & higher oil pressure.

 

[DJ]

Re: what is the best exaust? thru or prop?

Oop's

You have two threads going with the same question. Not good. Confusing. Your responses to your last thread are following. I am deleting your thread in "Boat Restoration".


whats better, thru hull or prop exaust?

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id doin a rebuild 19 foot. i/o 350 or 383. dont no yet.
b3 drive. am considering headers.
whats the difference, between thru hull exaust and standard prop outlett?

i hear marine manifolds are very good at letting an engine exhale.
am i going to gain any thing by going headers and thru hull?

thanks
oops


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#2 Today, 02:43 AM
SFT2
Seaman Apprentice
Join Date: Nov 2007
Location: Spring, TX
Posts: 42

Re: whats better, thru hull or prop exaust?

--------------------------------------------------------------------------------

Quote:
Originally Posted by oops!
am i going to gain any thing by going headers and thru hull?

Yep, noise


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#3 Today, 05:09 AM
Bond-o
Supreme Mariner
Join Date: Apr 2002
Location: The Mouth of the Chaumont River, Chaumont Bay, Ny.
Posts: 13,999

Re: whats better, thru hull or prop exaust?

--------------------------------------------------------------------------------

Quote:
i hear marine manifolds are very good at letting an engine exhale.

Nope,.......... Not True........

The current crop of center riser manifolds just dump the gases into a common cavity,.........
That in itself is a Major Restriction.........

But,...........
If you do in fact throw the Ma$sive Coin$ required for True Marine Header$,........
Then,+ Only Then will Thru-Hulls pay any sort of dividends in Horsepower.............
Otherwise,..........
You'll just be making Noise......................
__________________
Any Grease is Better,..... Than No Grease at All.......


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#4 Today, 06:20 AM
DJ
Moderator
Join Date: Dec 2001
Location: PHX, AZ
Posts: 14,849

Re: whats better, thru hull or prop exaust?

--------------------------------------------------------------------------------

The other guys are right. I have a 454 MPI/B3 in a Crownline with "Captains Choice". With the throw of a switch I can route the exhaust through the prop, or out the through hull exhaust.

There is NO difference in performance-just noise. I do have stock manifolds.

I have to admit that the through hull exhaust does sound pretty cool, especially at idle. I would not want it permanent though.

 

[Silvertip]

Re: what is the best exaust? thru or prop?

Not to mention a lot more noise!

 

[amynbill]

Re: what is the best exaust? thru or prop?

Thru is annoying unless you are away from the docks, restaurants, slips and anywhere people may be who do not wish to hear it.

There is more than likely very little gain in power.

Egotism at its best, IMO.

 

[Bondo]

Re: what is the best exaust? thru or prop?

Ayuh,........... Thanks for clearing this up DJ,......
This repost sets it up alittle better,.....
And,......
I get my post count back,..................

i hear marine manifolds are very good at letting an engine exhale.

Nope,.......... Not True........

The current crop of center riser manifolds just dump the gases into a common cavity,.........
That in itself is a Major Restriction.........

But,...........
If you do in fact throw the Ma$sive Coin$ required for True Marine Header$,........
Then,+ Only Then will Thru-Hulls pay any sort of dividends in Horsepower.............
Otherwise,..........
You'll just be making Noise......................

 

[Silvertip]

Re: what is the best exaust? thru or prop?

And then you need to add a "gigawatt" audio system so you can hear the tunes above the exhaust note. And on and on and on!

 

[Ride The Lightning]

Re: what is the best exaust? thru or prop?

Sorry, what is "Thru Hull"? Is it with a pipe letting the emissions out not into the water?

 

[DJ]

Re: what is the best exaust? thru or prop?

Sorry, what is "Thru Hull"? Is it with a pipe letting the emissions out not into the water?

Through hull exhaust exits the boat either through the transom or the sides. Non through hull exits the boat through the engine lower unit.

 

[45Auto]

Re: what is the best exaust? thru or prop?

You've got to be pumping serious amounts of air and gas (think built-up big block) through a motor before a thru-hull set-up does more than make extra noise and impress people who don't know any better. The vacuum created behind the prop supposedly helps pull exhaust gases out on the stock setup. You won't see any benefit from the thru-hull until you're pushing out enough exhaust products to outflow the area provided by the passages in the outdrive. I can't tell any difference besides sound on my stock 496 with the switchable exhausts. Supposedly it helps top speed a little. It does sound neat at idle though!

CORSA exhausts (makes thru-hulls) basically says the same thing in their FAQ:

From CORSA (these people MAKE thru-hulls, so you know they're going to make them look as good as possible!):

3. What kind of performance gain can I expect from a CORSA system?

Performance gains vary from boat to boat. Typically the top speed will increase by about 2-3 MPH, which means about a 20 to 30 HP gain. Boats with smaller engines (under 350 cu. In.) will not see much improvement in top speed.

http://www.marinemanifold.com/PARTSPAGES/Corsa/faq.htm

 

[oops!]

Re: what is the best exaust? thru or prop?

this is the kind of info i joined i boats for!

any way to open the restriction at the elbow? (on stock)
bigger elbow mabe?

thanks guys

oops