Was the 200 RPM increase in the spring? I went from Stainless Marine exhaust to Keith Eichert Exhaust and got the same results. When I first tested them it was in the spring and around 55-60 degrees. Once the weather warmed up I lost 200 RPMs and they were for the most part equal to the Stainless Marines. The only real difference was better midrange, top end was the same or very close.. This was on a highly modified engine not a stock 310 hp 454. I just find those results very hard to believe. Lots of other people have put on aftermarket exhausts on stock 454's and saw no gains at all, I don't see why the Dana's would be any different.

The stock exhaust on the 496 is pretty good. A free hp boost is to remove the tabulators, I think thats good for about 10 hp. If it were me I would save your money as Mr.Fixx All suggests. Send your props in and have them labbed at BBlades. You most likely get more of a gain out of that and it will be a lot less $$$$$ out of your pocket.

The only Dana header manifolds I have ever seen or heard of are cast at BuddyBar in Los Angles, California , same company that casts parts for Merc, Ilmor ,Imco and many others in the marine industry. I have not heard of any of the 496 dana header kits having any water intrusion issues unless someone was using to big a camshaft and had some reversion issues.

Best Regards,
Ray @ Raylar

If you haven't read it, here's a link to some good testing I did on a 496 HO with Dana exhaust.

http://fullthrottlemarine.com/496%20...%20Article.htm

Bob Lloyd
Full Throttle Marine

yes that was in spring with water temps in the low 50's and air temp around 70, i'm not trying to b.s. anyone all i know is that boat ran consistent 66 @ 4700 with a mirage plus 23 and ran 67 @ 4900 with the exhaust on, so i switched up to a 25 mirage plus and ran consistent 68 @ 4600, perfect conditions and light fuel it clicked 70 once in awhile, i don't see how the weight savings between the two, the better flowing exhaust, and a bigger prop would not be alittle faster

bobl so your testing on a 496 ho with dana exhaust states that it does not produce 40hp ? spoke to raylar the other day and he claimed 40hp gain and on my twin application a toatal of 80hp with a gain of at least 4mph and prop change ? is this not possible ?? boat is a 2002 31 sonic.

I put a set of Danas on my outlaw. With stock merc exhaust boat ran 63mph at about 5200 rpm, with the Danas, 64 mph bouncing on the rev limiter! ( 23 mirage and yes, GPS. Stock 385 mag)

river monkey am i correct in saying your engine you put the dana system on was not a 496 correct?

[QUOTE=

The stock exhaust on the 496 is pretty good. A free hp boost is to remove the tabulators, I think thats good for about 10 hp. If it were me I would save your money as Mr.Fixx All suggests. Send your props in and have them labbed at BBlades. You most likely get more of a gain out of that and it will be a lot less $$$$$ out of your pocket.[/QUOTE]

can you please tell me wot the risks are if you remove the tabulators , i am not sure but are they not there to stop water and condensation from running down into the ports ? i am sure i read this somewhere. regards paul

It's the variables in the test method. Ray tested them with the tips running dry since their dyno did not have the ability to collect the water out of the tips. Mine is designed to run water all the way through the tip just like in the boat and of course while prop testing it is installed in the boat. The wet exhaust can easily cost 20+ HP, but that's the real world unless you run dry tips on your boat. So, neither test is wrong, you just have to "read the fine print".

Bob Lloyd
Full Throttle Marine

yes they are there for condensation, the boats with switchable exhaust, kept in the water, and colder climates have the higher risk of the valves rusting, how much idle time before shutting engine off and how fast you come off plane also have effects, as does the routing of your exhaust exiting the boat