Here is my solution to the CMI leaking problems....Stellings! I decided to go with Stellings simply because I have had them on other boats without any problems. I got this current boat in April and ran it this past season with the CMI headers all the while keeping my fingers crossed and constantly draining them as a precaution. I didn't have any problems with the CMIs, but I didn't want to keep using them due to their track record.

This past fall I ordered a set of Stellings headers and tailpipes from Benfield's (Stellings dealer) to replace the CMIs. We have just started the install, but we have not finished it yet. We got all of the old stuff removed and the new headers on before it started raining, but we still need to install the new tailpipes. I'll post some pictures when it is finished.

Thanks Hot Duck, I like the stellings, but I don't think my Corsa diverters will fit. Looks great keep us posted. Doug

I have had a few questions on this topic, so I will post my thoughts here as well. I don't think that CMI makes a bad product in general. From what I understand and from what I have read I honestly think that the problem comes from the parameters and requirements that Mercury gave them for these headers. I also think that the problem is with this specific header design and not with CMI in general because they do make some nice products. I have had CMI headers on other boats (as well as Stellings) and have never had a problem with them. The CMIs on my current boat have not given me any problems, but with all of the failures reported on the 525s I wanted to change them out just to be safe.

Hot Duck you appear to have some kind of mufflers on your boat, what kind are they? Do they quiet the boat some? How big are the motors? Did they affect your speed much?
Thanks Steve

I posted early on in this thread with issues that were thought to be related to the failure of CMI headers on my Small Block Ford in a Donzi Corsican.

After a bit of work and some valuable support from the crew at CMI , and the dealer that sold these to me, Ateco Engines, we found the cause for the water I discovered in my exhaust ports and header tubes.

My engine is a built 400 HP 302 cu in Ford. These headers as built have a very large internal volume, and the water injection point was to close to the elbows at idle speed.
Another way to view this is that at idle the exhaust flow rate is so low in the large tubes to fully carry the water out to the transom . . . we added water outlet tubes inside the collector to inject the water further downstream and CMI supplied me with a set of anti reversion cones to install.

Water reversion can happen from water literally migrating back against the exhaust stream at low engine speeds by "wicking" along the tube walls. This happens when the cam overlap is too much and or the exhaust flow area is larger than needed . . or both . .

So I did not have issues with CMI, or their product, but challenges with a small block Ford in a boat application where there are only 2 manufacturers for headers world wide, and the other company doesn't count!

Now just what will I install in my twin engine SBC Magnum 27??

Mario L.

1969 Donzi Corsican
1968 Magnum 27

We appreciate the support Mario!!

It does have mufflers on it, but I don't know what brand they are because they were on the boat when I got it. I'll post a better picture of them when I get home tonight and maybe somebody can tell us where they came from.

These mufflers do make the boat substantially quieter, but they still yield a nice low rumble at idle and while moving. They basically take the "rasp" out of the exhaust noise and make it sound more like a muscle car than a boat running open headers.

For power I am running Merc 525s. As for the speed, I don't know if the mufflers hurt the top end or not because I have never run the boat without them.

Here is a video if the boat starting at the ramp.

http://media.putfile.com/Cig-39-2

You can't hear much engine noise because of the wind, but here is a short video of the boat up and running.

http://media.putfile.com/Cig-39

Will, when I sold the F-2 it went to the left coast.
I flew out to long beach to run it for him in the SCOPE poker run.
He put mufflers on it & during the run the boat ran 7 mph less.
I tried everything I knew to get more speed...... but couldn't

Robert,
I did use a couple sets of Hardin's headers(Hurricanes, I think) on some 1200efi's that I built. I could not be happier with them. I do not know if they make them for the 525, since the flange is different. If they do, I would not hesitate to use them.
Eddie

So has the problem been resolved with the newer 525's? If so what year was it changed, fixed?

Hot Duck - sharp boat!!