Exhaust Upgrade

[Blue Mist '97]

Gentlemen:

I have a completely stock 454 mag (1997 Gen V, I believe) in my Persuader 261. I have been thinking about upgrading my exhaust for a while. Problem is, I have not done any engine work in many years and have forgotten most of what I knew.

I am considering purchasing a set of Imco PowerFlow exhaust (for BB) and standard A risers from Needafunboat (Anthony) as posted in his thread yesterday, for my boat. My questions are as follows:

1. Is it worth the time and trouble to upgrade the exhaust from original to the Imco?
2. What will I gain or lose?
3. Will the standard "A" risers work (as shown in his thread from yesterday)?
4. If not, what risers would work best?
5. Should I change out the tips also, or will the OEM work?
6. Suggestions on tips if I replace (would really like to have some cooler tips)?

Sorry to ask such elementary questions, but as I stated before, I am trying to re learn how to do my own work on motors. I have attached a few pics of the current set up so you guys can sound off.

I appreciate any help and info that you could throw my way.

Thanks in advance

BM 97

 

[Gimme Fuel]

Those IMCO manifolds are nice and you should notice a big difference with them on if you get rid of your Corsa Quick & Quiet setup. those things were power killers. Powerquest loved to put them on and the baffled tips they come with are very restrictive. Most with PQ's that got rid of that system alone gained a couple MPH. Those A Risers are a nice option but won't work with the Corsa setup you have. The other issue you will have is I see your stock exhaust has a 3" block between the riser and manifold. You will have to also put a 3" spacer (one you have won't fit BTW) between the IMCO manifold and riser to line up with your existing transom exits. You can either have a buddy with a machine shop make a set (seeing as it is a dry joint between the pieces, or IMCO probably makes one. The other option is to send the risers back to IMCO and they will cut off the flange and add 3" of pipe in there. As far as tips go, I would go with a nice set of IMCO or Hardin tips with internal clamshell stainless flappers. Way better than the baffle system Corsa's tips use to prevent water backing up and much less restrictive.

 

[Blue Mist '97]

GF - Thanks for the info. I did find that IMCO makes the "A" riser with a 3 inch rise and also one with a 6 inch rise. I would assume the 3 inch would do the trick, but will check to make sure before I order. I will probably order them next month and get ready to hook 'em up over the winter.

Any suggestions where to order to get the best deal?. Looks like most places I have checked are all within $100 or so of each other.

I think I will install some long angle tips to finish it off as well.

Thanks for your help.

BM

 

[Gimme Fuel]

I see you have a block in between your elbow and manifold. If that block is 3" high, you will need the 6" risers.

Post a pic shooting the direct side of your manifold to be sure. The top angle makes it hard to tell exactly.

 

[Blue Mist '97]

Ok. I gotcha. Will get a couple of pics when I go up there this weekend or next. Just by what I remember, it does look like about a 3" block, but I will measure to be sure. Didn't realize that the block was an additional 3". Thought it was just 3" due to the block. Glad you told me.

Thanks for the heads up. Will get back with pics shortly.

 

[Blue Mist '97]

Hey GF

Here are a couple of pics of the exhaust that you asked for. Sorry for the poor quality but I took them with my cell, laying over the rear deck and hanging down in the motor well.

I do believe that the blocks are 3" but just estimating. Thanks for pointing that out, as I would have probably ordered the 3" risers instead of the 6" set.

I am curious, however. Are the Imco manifolds taller than the MC OEM manifolds? They look like they are, but I have only seen them in pics.

Anyway, thanks for your help.

Pat
BM 97

 

[Gimme Fuel]

That is a good question. I know someone who has that same manifold setup on a 251 and bought a set of take off 496 merc manifolds on the cheap. Perfect fit. Im thinking the taller imco manifolds and the standard riser will put you where you want to be. Just measure from the bottom of manifold exhaust port on block to top of riser. Tell that to imco when you call and they will tell you for sure.

BTW if your engine is stock and you dont plan on juicing it up, the take off 496 manifolds bolt right up and perform similarly on stock motors to the aftermarket ones. They are one of the best manifolds merc ever made and the bolt/port pattern is same as older gen 454/502. If you are going to mod in future go with the imcos

 

[Blue Mist '97]

Decided to call Imco this morning and ask a few questions. They told me that the Imco manifold is taller than the OEM manifolds, thus that additional height compensates for the 3" block between the manifold and riser. They did say the same thing that Gimme Fuel said earlier, that I should see about a 10% increase in hp and more torque.

They also said that the 3" riser is what they recommend for OEM design upgrades.

Now to really start looking for a deal. Not sure if there are any good deals out there. Most appear to be about the same. If anyone knows of one, please let me know.

Thanks

 

[Gimme Fuel]

You csn get take off 496 manifolds complete for 500 or less on oso or ctaigslist. Other than that, just gitta keep eyes open. Always stuff for sale on offshore only

 

[Blue Mist '97]

Ok, so I bit the bullet and ordered a new exhaust system. Was down to Imco and Lightning. I really wanted the Lightning headers, but decided to go with the Imco exhasut with the 3 inch taller "A" risers. Also ordered a new set of Imco tips. Should be ready to go this fall.

I will have a complete set of OEM exhaust manifolds and risers (with the 3 spacers) for a 454 mag available if you know someone in need They are old, but have never seen salt water. If they are bad, I will junk them.

I know that very few, if any, would need or want it, but I will also have a complete Corsa Quick and Quiet system available. It will include the silencer tips.

Also looked at a new DUI ignition as well. They are adding an all new new built in adjustable rev limiter for their distributors this fall. Should be nice. Don't know how much improvement it will make now but it should help out some.

Thanks for the help.

BM 97

 

[Blue Mist '97]

Got the new Imco exhaust stuff in and it looks really nice. They sent the wrong risers (standard instead of the 3"taller), but one phone call to Dave at Imco and he shipped me a new set out that day with no questions asked. Kudos to him and Imco for taking care of their customers promptly.

Will begin the process soon to get rid of the cumbersome old OEM manifolds and risers and the Corsa Quick and Quiet system. Then, clean everything up and get these new manifolds on and ready to go.

Everything looks pretty straight forward for the install, hopefully it will go pretty smooth. If there are any problems, I hope that I can lean on you guys for some helpful advice.

Thanks

 

[Blue Mist '97]

Progress

Well, this little winter project install isn't as straight forward as expected. Have installed the starboard exhaust manifold and it's ready to go. Problem is the 3" taller riser is too tall. Riser is about 1 1/2" too high at the rear and makes for a connection that is off by about 1 1/2" - 2" and at an odd angle (see pics). Everyone that I have talked to, including Imco, says that the OEM exhausts and risers with the 3" spacer should use the 3" taller risers. Original measurements confirm same, but it is a no go.

So Imco sent some cardboard riser templates (wish I had known that they had these to begin with) to measure correctly and get the right height and length for the risers They said that they would make sure that they get it right for me. Of course, getting it right means that it will cost a little bit more to make them custom.

Also, I am beginning to think that the standard risers might possibly work, since the Imco manifolds are taller than the OEM manifolds by about (yep, that's right) 3" or maybe 4". Well, just for fun I decided to set one of the 3" taller risers onto the still attached port side OEM manifold, w/o the spacer block, and it appeared to line up with the tip almost perfectly. I wish now that I hadn't returned the "wrong" standard risers that were initially shipped, so I could try them.

Every time I start a new project, I try to learn something from it. The lesson I learned in this project so far is, that no matter how big the engine compartment looks from the outside looking in, it ain't that big when your inside trying to do some work. It's hard on a big guy's knees. I don't know how guys with twins could ever work on their motors. My hat is off to them.

 

[keith4216]

Its always fun doing custom work.
Your pic shows the port side connected not the starboard. Hope that didnt make a difference.

 

[Blue Mist '97]

Correct. Port side is still connected in the pic. OEM riser and Corsa Q&Q is now gone, but OEM manifold is still on. Heading back up to work on it next week.

 

[Blue Mist '97]

Progress

New manifolds installed. Measured for the new risers with the templates sent by IMCO. Going back up one more time this week to make sure the templates are good good to go before re-ordering. Also have the new IMCO tips sitting in the transom. Will finish tip install this week.

Below is a pic with the port side template in place. Went up Saturday and double checked to be sure of measurements and decided that they needed another 1 1/4" in height to line up straight with the new tips. Made a new set of templates and will order which ever one lines up better.

Also a pic of the old tips and the new tips. I like the look of the new tips much better than the old Corsa tips.

What do you use to clean your motor compartment and bilge with? How do you clean it? Thought about pouring some bilge cleaner in with some water and towing it home so I can really clean it up, then drain it and scrub the floors. Better suggestions?

 

[corey331]

Honestly, I have always just used Dawn dish soap to clean my bilge area. That stuff cuts grease and grime like no other. I just get the area wet, dump some dawn in there and let it set. If there are some really dirty areas I'll hit them with a scrub brush, but for the most part, after letting it soak, you can just hose it out and most of the gunk comes right off.

 

[Kurtster]

Hey Pat ----- hope you had great holidays down there in the big state

Love the look of the new tips --- much nicer than the Corsa's.

Having an engine compartment as clean as the one in your Persuader can probably be done nicely "as Corey says" with a nice dish soap like Dawn {I prefer lemon scent }

A typical bildge cleaner works well for the real dirty spots but I try and avoid the harsh chemical stuff as much as possible.

BTW --- did you ever hook up with the "windaway" product stuff ?

 

[Blue Mist '97]

Thanks for the info guys.

I will try that and see how it works. Well, they say that Dawn cuts grease so we will give that a shot. Do you cover all the trim and tab stuff? Not sure, just how water proof they are.

Kurt
We had a great holiday. Grandson's first Christmas. Hope you did too.

Actually no, I sent an email and never heard from her. I don't have her address anymore (did a major email dump and deleted it). If you still have it, would you mind shooting it to me again?

Pat

 

[Blue Mist '97]

FINALLY!!

Got the new "custom" risers last week from Imco. They built them via the templates that I sent them. Not too bad, only a 5 day turnaround on the build and 4 days shipping.

IMCO ran the water exits out to within 2"-3" of the back end of the riser, which is much further than the original risers. These risers matched up pretty dang close (not perfect, as I was the one doing the measuring, but close) when installed. There is 2" of open space between the end of the riser and the exhaust tip.

Installed - IMCO power steering/alternator relocation bracket, so high pressure line would clear the manifold. Also, had to cut a slot in a small brace for the power steering pump so it would bolt up to the pump and secure it. Have to say other than that, it matched up perfectly and put all the belts right in line. Old belt still fit, but was at the end of the adjustment slot, so I installed a new belt (Gates XL V Belt #7555), 1/2" shorter. Perfect fit.

Installed - IMCO shift bracket - Had to drill one hole in the IMCO shift bracket so the lower unit oil reservoir would bolt up. Other than that, perfect match.

Had to guesstimate the length of the exhaust hose when I ordered, so I ordered 7" and IMCO sent them 7 1/2" (for good measure) each, but had to cut them down to 6".

Everything went in and on very smoothly today. Much better than I thought it would. Had a couple of small issues, but resolved them and continued on. All in all, it was much easier than I first thought.

I would like to thank Dave Hards @ IMCO for his help and patience. He is very knowledgeable and helpful. If anyone ever decides to install IMCO exhaust, or new drives, he is the guy to talk to. There is a long story to the original purchase of these manifolds/risers and Dave was gracious enough to take care of everything and make it all work.

Enough of this dribble. Here are a few pics of the final install. All that is needed now, is a water test, some pre spring checks and a lot of cleaning, especially the bilge area and motor compartment.

This old guy is tired, so tonight is going to be a Crown Reserve kinda night.......

Thanks to all
BM97

 

[keith4216]

Looks very nice.