Performance Boats Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
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
 

·
New here
Joined
·
4,219 Posts
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.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #3
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.
 

·
Registered
Joined
·
5,180 Posts
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.
 

·
New here
Joined
·
4,219 Posts
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:
 
1 - 5 of 5 Posts
Top