bajamann

Has anyone had success with CMI headers over the long haul? I am in the process of refreshing my 2004 525's in a 353 Formula, and am trying to be as thorough as possible. I have 300 hours of fresh and saltwater use. In the process, I pulled my 10 year old stock CMI headers and water-pressure tested them- no leaks. I am also performing the water flow mods recommended by merc and CMI. After reading the posts on the OSO forums, you would think every set of CMI's resulted in catastrophic engine failure. It seems that staggered setups are more prone to cracking. I would suspect that overheating is also a culprit. When mine were disassembled, I found a piece of heat exchanger gasket totally occluding the bypass to one of the tails, but fortunately, this is a passage that merc suggests blocking. Just curious if it is 10 or 20 cases of failure, or if this is a systemic design flaw that will result in failure sooner or later. Need responses before I put em back on!

SFOcean

iTrader: (1)

Yep; 2001 and 2003 sets on different boats, both still air test no leaks. They both have full time drains so they are dry any time the engine is not running.

Biggus

iTrader: (1)

My '02 Cigarette, 575SCI's, has the original headers. Fresh water, no leaks. I do drain them when the boat is trailered or not going to be used for a while. Also my old Top Gun is still running the same pair of CMI headers (E-Tops) installed in 2000. Still working fine.

HyFive578

iTrader: (3)

It's definitely not a few isolated cases. It was a systemic design flaw in the headers from about 2003 to 2008 but not everyone has a failure. Overheating definitely a contributing factor but so is the amount of flexing the headers undergo as that puts stress on the welds as well. You should consider yourself lucky. There is no rhyme or reason as to when they will fail, and they may not but at 10 years, its a gamble.

brian41

iTrader: (1)

I have had and still have several sets with zero problems. All are fresh water boats that we rigged with proper fitting tail pipes with no stress added to header because of misalignment that we see all the time even on factory rigged boats.

thirdchildhood

iTrader: (6)

'07 vintage 525 with original headers still fine.

302Sport

Flushing, then draining before putting boat away for the week is a major plus. If you do this and happen to get a little leak over the course of the season, your engine will most likely live and when you pressure check in the fall, you can fix the issue. Almost all of the major problems occur from people not draining the headers, cylinder fills with water, sits for awhile, then when the starter is engaged, you have a major issue.

bajamann

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I agree. I am planning on putting together some type of single valve drain system so that I can easily drain both sets of headers without taking 4 blue caps off. I only plan to drain when putting the boat away for the day, after the headers have had time to cool. May even install a hose connector to quick flush the headers without cranking engines. Problem I have run in to is front drain on collector is not an npt thread, and I have not been able to find a connector to attach to it.

HyFive578

iTrader: (3)

I wouldn't recommend flushing the headers without running the engine. You want the pressure of the pump pushing the water to flush all of the cooler components (oil, fuel, heat exchanger), the headers and out the exhaust. Without the pump running, you run the risk of having pressure build up and if you do develop a leak that you haven't discovered yet, you could force that water into the cylinders.

You don't need to pull all of the blue plugs. You can install a draining system on the rear 3/4" female ports where you remove the elbow connected to the bypass hose.. and by the way, the bottom rail is called the distribution rail, not the collector... the collector is at the top of the header where the four tubes "collect" to send the exhaust/water out the tail.

As for the draining system, there are a few good ways to do it. Just search for "header drain" and you will find my solution which is a manual ball valve that drains both headers on the engine at once and you will find others that have a small line that drains to an overboard dump automatically when the engine shuts off. Leave the front blue plugs alone.

HyFive578

iTrader: (3)

Lot of this ground covered here...myself and others detailed our respective draining solutions.. all work well. just a matter of preference... want to drain yourself or let the system do it for you...

http://www.offshoreonly.com/forums/g...er-issues.html