KE Headers on 525 EFI
 

Has anyone swapped out the CMI/Merc exhaust that comes on the 525 with the Thunder and Lightning exhaust from Diamond? I just bought a boat with 525's in it, and I really don't like the idea of these headers on the engines. Yes I know the heads will need to be drilled and tapped, but other than that, would any other modifications need to be done?

Not sure why you would have to drill and tap your heads, I was going to use them on my boat but the transom holes needed to be moved so I went with Stellings. The only concern would be adequate water flow and would suggest a water pressure gauge if you don't already have them as the KE's are aluminum. I bought the KE's because the power curve was better than the Stellings but, redoing the transom wasn't worth it to me. I have been told they sound great and I like they way they look (sleeper). If you go that route I would be interested in how you like them. Oh, salt away flush after every use since they are aluminum.

Because the 525EFI heads have a sightly different exhaust bolt pattern.

Go with the Stainless Marine setup. It's not as pretty as full headers, but they are a proven product with plenty of happy customers.
AT installed a set on a 37AT with 600SCis and not a single change in performance. (That boat is in Indiana now.) They aren't as pretty, but I'll take reliability over pretty any day of the week and twice on Sunday.

If it were me, I would paint the 'manifold' portion silver to match your boat, and I think the contract with the Mercury blue would look awesome. And it's less cleaning/polishing to do back there too.

Clark aka "crb76" was the original owner of your boat. He's one of my closest friends and posted a fair amount here on OSO when he first got it. His dad, "chuck beecher" here on OSO was also quite active at the time. Chuck purchased a 32' from Pat/AT way back in the day, so it was awesome when Clark purchased a 37'. Your boat has been 90.1mph with a set of Herring high end props in it back in the day. It's also the smoothest riding and most solid 37' AT I've been in to date. I have a lot of hours driving and riding in that boat from when he owned it from new.

You have a helluva boat. I was quite tempted on purchasing when it came up for sale, but I am now having to much fun racing cars.

Sydwayz- Yes I think "Stealin' Thunder" is one of the nicest looking 37's I've seen. I wasn't really in the market for a new boat when I first saw it, but it was in near showroom condition, and I absolutely loved everything about it. Well other than the headers that 525's come with. I knew I wouldn't find another one like this anytime soon, so I jumped on it. Everything was finalized this morning! I'm glad you have good things to say about the boat.

I'm really leaning toward the Thunder and Lightning setup as I've run them back to back on NA boats and did see an improvement over the Stainless Marine manifolds. The Stainless setup is nice and reliable though. If I have to relocate things with the Thunder and Lightning headers, I'll go the stainless route. And yes, I will be having them powder coated silver, I agree it would match the boat and look great.

I talked with Bill today, outside of drilling the standard bolt pattern in the heads, he said everything else will be exactly as it is now. I've had custom tales made before for K/E headers. With the flanges you can buy from Bill, it's mostly just a straight back set up, at least my last set was. I think I may go with Teagues 450 switchable tips so I can retain the selectable exhaust. If that is the case, the tails will be pretty short.

If I could find a good deal on a set of Gen X headers, I would think about going that way, as it would be the easiest way to go. However as it is, Thunder and Lightnings are half the price and equal or slightly better performance.

I recommend Diamond / Bill exhaust and I will tell you why. I have worked on Volvo DPX 600 engines and had a twin app with full CMI headers - one side CMI were leaking as I CHANGED in time. That owner ended up buying at that TIME were KE currently Diamond / Bills exhaust and there was NO Drop in speed or performance period. I know because I drove and maintained the boat every year.

https://cimg9.ibsrv.net/gimg/www.off...b8b4370d22.jpg
https://cimg1.ibsrv.net/gimg/www.off...bc9d04377a.jpg
The K/E Headers will fit the Merc 525efi -

Bill-

Those would sure look nice painted silver and attached to my engines!

Changing plugs with the T&L headers is better than Gils, Gils are the worst.

That is Manages 27 Activator with the 525 wonder if will chime in as for speed number differences or whatever.

Endeavor32: Make the beginning of the KE/Diamond tails to the end of the tips 18"-20". 19.5" is ideal. Your welcome. :)


---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----
1st Harmonic = 155.2 inches long ... longest with Mufflers and TailPipes
Note: Worst = 116.4 inches long for HP/TQ Loss
2nd Harmonic = 77.6 inches long ... longest recommended with Mufflers
Note: Worst = 58.2 inches long for HP/TQ Loss
3rd Harmonic = 38.8 inches long ... more bottom-end Torque
Note: Worst = 29.1 inches long for HP/TQ Loss
4th Harmonic = 19.4 inches long ... highly recommended , best Torque Curve
5th Harmonic = 9.7 inches long ... reduced Torque , more top-end HP sometimes
6th Harmonic = 4.9 inches long ... reduced Torque , not recommended

Thanks SB!