Curious obout header issues
 

I've noticed that there has been a lot of complaining about the CMI headers used by Merc for their 525's. I have a couple of questions:

What is the actual problem?

Does the problem also exist with the 575's, 600's and 700's?

Sounds like there can be significant damage caused; how bad can it get?

Is this something that happens with all CMI headers on Merc products or even on the custom engines?

What does Merc do to solve the problems?

There are plenty of other header manufacturers out there; is this a CMI problem of a casting problem with the heads used by Merc? For example, does this happen with Stelling?

Bottom line:
CMI spec'd a header for the 525EFI for the OEM package.
Mercury didn't like it. They wanted something different. (read: cheaper)

CMI made the headers that Mercury wanted, per Mercury's factory specs.
They did not hold up over time, usually just long enough for factory warranty to expire.

CMI got the bad name/reputation; but not their fault.

CMI's 525EFI headers, that you buy directly from them do NOT have this problem. They are of a different design, spec, and quality. (read: better)

Staggered boats are most easily affected, specifically the forward engine which allows more movement of the tailpipes and headers; allowing the welds to crack; and leaks to take place.
HOWEVER, many, many side/side boats have been affected too.

Also I believe for the most part the years when the problematic headers were produced were in the 03-06 range?

you can destroy an engine if water gets in a cylinder and you hydro lock it...

Sydwayz has it pretty much covered.. Inferior metal alloy used on earlier model 525 headers caused cracking in the welds, causing water ingestion into the engine.

Does the problem also exist with the 575's, 600's and 700's?...

>>> It occurs on 525EFI's, 600SCi's and 700 SCi's as they all use the same header.

Sounds like there can be significant damage caused; how bad can it get?

>>> If they leak and not caught, best case scenario is stuck valve, worst case scenario is hydrolock the motor and say goodbye...

Is this something that happens with all CMI headers on Merc products or even on the custom engines?

>>> This really only is relevant to the MERC spec CMI header; CMI headers that are purchased from them directly are not the same spec. Pre-2004 Merc/CMI headers were the worst.. 2004 - 2008 better but still prone to leaks, post 2008, the spec was changed/improved.

What does Merc do to solve the problems?

>>> Not much...

There are plenty of other header manufacturers out there; is this a CMI problem of a casting problem with the heads used by Merc? For example, does this happen with Stelling?

>>> Has nothing to do with the heads; it's the metal that was used. Not a lot of reports of failure with Hardin Marine or Stellings. I was under the impression that Stellings is out of business.

Thank you guys. I'm always amazed with companies who tout their products as the best, put inferior products out for public consumption and ignore the problems that their pizz-poor decisions cause.

If you can switch to stainless marine cast manifolds I would, they make the same power and never leak. All tubed headers will leak at some point, just a design issue.

It's not specifically a CMI thing, its a header thing... All headers will leak, just some take longer than others.

For what it's worth I am running CMI's manufactured in 92.

Yes to all the 525 Merc spec stuff mentioned above.

With all headers, they should be pressure tested regularly to check for leaks.
Also, I have added header drains which help prevent water laying in them and possibly leaking in while sitting.