New exhaust question.
 

I'm considering replacing my stock cast iron exhaust manifolds with some lighter and better flowing after market manifolds. I'm running a 97 PQ 26' with stock 454 mag EFI w/400 hrs. Engine runs very strong as we cruise for the most part. At best I'm seeing 60mph tops and would like to see a tad more. I've read that making the change in my size boat will yield 3-6 mph. I do have silent choice and do plan on keeping it. Looking for suggestions on what brand would be best suited for my situation.

stainless marine
rev marine
eddie marine

I had good luck with the EMI thunder manifolds with the stainless short risers[for capt. call] I installed on my old 29 outlaw i use to own, it had 454mpi mags in it, I picked up almost 2 mph

You won't gain speed everytime with an exhaust swap. It depends on a lot of factors. If you are planning any future HP upgrades. the exhaust is the best place to start. It will most likly make anything else work a little better.
If you have a good breathing engine already you may gain 10hp with the swap. That will equal 1mph with twins. Or, if the engine is starved for air now, by improving the exhaust you will lose a little back presure. You may actually lose rpms untill you take care of the starvation issue.

I'm putting the cast aluminum 496 exhaust into my legend along with an engine upgrade. I got these used and powder coated them. They look great and I'm told will be almost as much gain as I can get out of exhaust unless I put some serious HP into it. Might want to step up to something more expensive if you plan to put $$$ into the engine in the future but for the $400 I paid for these I really can't justify another $1K-$2K for something better.

There are a lot of threads on here about these if you do a search. I've taken measurements, and I think they will fit with my captains call with new hoses and some maneuvering. Will have to relocate the cable bracket to somewhere else.

3-6mph gain........No way. A 1-2mph gain.......maybe.

It will sound faster, that's worth somwthing:cool:

I have a pair of these and might not use them because I am in salt water, and am getting another parts motor soon.
They are fresh water and complete 2004 low hour removed apx 2 years ago. Pm me if interested
You have alot of great options in the Fresh water where as you don't have to buy Cmi Stainless, Tailpipes and thier stainless Diverters.
I also Have a Fresh Water Merc Factory set of Gils at a local shop were being fixed Water hoses were hooked up wrong and they cracked. Hope this helps, BBB

If thinking about motor mods later, you might want to think about dumping the silent choice.

No real plans on mods as I want to keep her turn key with no issues. I'm not sure how long we will keep the boat as well as I've been doing a little shopping fore something larger. My only drawback is my 1/2 ton pickup. If I do decide to make any mods I'll more than likely swap out the 454mag with a 496 HO or something else along those lines.

As far as getting rid of the select choice thats out of the question. I have a family and thats about the only part of the boat the wife likes. If it were up to her we'd have a cruiser...
And I just can't do that..

I had read in I belive powerboat a while back on exhaust changes and they were reporting pretty good gains on single engine boats .

I agree. Alot of coin for that.

If you plan on doing any other work to the engine I would seriously consider true header exhaust.
Be very carefull of aluminum exhaust.
If you overheat the engine due to lack of water flow the aluminum exhaust can melt down.
The headers ( steel ) will usually survive this.

Dana marine manifolds!

I have EMI exhaust and I am very satisfied. Expect 1 or 2 MPH gain. This is the best place to start with the upgrades. You get rid of the wet riser joint and improve reliability. Any engine mods you do, especially the Cam would need them anyway. It is better if you ditch the silent choice, if you want to reduce the noise use mufflers to compensate.
Good luck!

I agree with Griff. 1-2 MPH gain at the most.

I replaced my heavy azz stock exhaust last yr with SM. Lost a good 80# between both motor change overs, but seen zero speed gains. Motors have a different sound now. More of a tingy sound now than the deep tone the cast steel gave it.

My previous boat had a blower motor with straight thur hull Merc/Gill exhaust. I got tired of the fulltime loudness real quick. Installed silent choice, had no speed loss.