454 Mag Outdrive Exhaust Converting to Thru Transom Exhaust ??
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454 Mag Outdrive Exhaust Converting to Thru Transom Exhaust ??

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    Junior Member bertus951's Avatar
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    Default 454 Mag Outdrive Exhaust Converting to Thru Transom Exhaust ??

    Hello Everyone,

    I currently have a 454 Mag that has the exhaust exiting through the outdrive that I was thinking about converting to through transom exhaust. Is this a complicated process? What kind of headers would have I have to buy for an I/O to go to through transom exhaust? What would happen to the exhaust port coming through the out drive? Is there a plug of some sort that is sold that is used to block water from coming in? What kind of HP gains would be achieved or lost? Any help is greatly appreciated.

    Thank you!!!

    Bertus

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    New here Beer:30's Avatar
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    Quote Originally Posted by bertus951 View Post
    Hello Everyone,

    I currently have a 454 Mag that has the exhaust exiting through the outdrive that I was thinking about converting to through transom exhaust. Is this a complicated process? What kind of headers would have I have to buy for an I/O to go to through transom exhaust? What would happen to the exhaust port coming through the out drive? Is there a plug of some sort that is sold that is used to block water from coming in? What kind of HP gains would be achieved or lost? Any help is greatly appreciated.

    Thank you!!!

    Bertus
    Yes, there are caps made for the tops of the "Y" coming up from the base of the transom assembly. You can also get "Captain's Call" exhaust valves that electrically open and close diverters so you can EITHER run through prop or through transom at the flick of a switch.

    That being said, you will not LOSE anything. You will GAIN significant HP/TQ. Your 454 thinks it's a about a 400 right now. It will be like an engine swap when you do this. You're probably leaving 40hp on the table right now, if not more. You'll will more than likely need the next prop up, depending on what max RPM you are spinning now.

    Your mileage will go up as well. Some of your spent gasses are backing up in the cylinders during every cycle, which contaminates the next intake charge / power stroke. On the SAME FUEL BURN, you will will gain a handfull of MPH.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Junior Member bertus951's Avatar
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    Thank you for the feedback. I thought that if anything I could gain some HP because of the restriction placed on the exhaust going through the outdrive. Do you have any recommendations on what headers to get, or maybe a website that will have the stuff needed to make the swap? I tried looking in the parts forum, but I don't know exactly what headers to look for and most of them seem as though they are for a jet application, not an I/O.

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    Senior Member EVILFORCE's Avatar
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    Captains Call is nice. If I am running exhaust out the drive and switch to thru the hull it picks up 50 rpm. Mine comes out the sides in the back. Do not know how much HP difference but I get 50 rpm with no other changes. I would install the switch.
    No Fool Like A Old Fool is there?

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    New here Beer:30's Avatar
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    Quote Originally Posted by bertus951 View Post
    Thank you for the feedback. Do you have any recommendations on what headers to get, or maybe a website that will have the stuff needed to make the swap? I tried looking in the parts forum, but I don't know exactly what headers to look for and most of them seem as though they are for a jet application, not an I/O.
    I like the scavenging of a tubular-header, myself. Almost ALL of the exhaust systems are doing a great job. ANYTHING other than stock is going to gain you more efficiency, so it's really about how much $ you want to spend AND If you care what it looks like.

    Here's mine, luckily found them used with 10hours, specifically for my engine (496HO with exhaust sensors). I paid $2000, shipped:
    Last edited by Beer:30; 05-23-2012 at 08:30 PM.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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