OSO CMI Header Education
 

I want to thank all the OSO 150 replies about the problems CMI & Mercury Racing are having with their 525s Headers. What an education, Both engines have been rebuilt because of the leaking headers, and now, I must decide on which new Exhaust Headers to buy. Thanks for the :readinghelp:

Rocker Down

Why don't you just buy the big block headers from cmi and take them to have'em drill an extra hole or two in the flange?

In other words, the non-525 headers are fine. It will take longer to setup then to drill the holes..

Gen-X ????? Maybe next time Merc will leave the header specs to the header folks.....

I replaced mine with Gen-Xs and am very pleased. If you have staggered motors, most likely will need to brace one motor.

stellings

I surely wouldn't buy CMI's if you starting over.

drill & tap your heads for stainless marine exhaust & be done with it.

X2 on the STAINLESS MARINE !!!!!!!

Fixx
 

+1,,,spend the xtra coin on the stelling's..

why are we into an other thread about this product......
you want them to last......
TAKE THE TIME TO WARM THEM UP!!!!!!!
TAKE THE TIME TO WARM THEM DOWN!!!!!!!!!!
IF YOU NEED A LESSON ON METALLURGY
i only charge 65 an hr
no seriously.....CMI are a reasonable product..... for the average hp boater
the problem occurs with temp..... overheating of the welds and rapid cooling of water injection at those points
stellings are a better product.... and if you pay $4000 for CMI you will pay $8000 for stellings the math is quite simple
if anyone needs a more detailed diatribe PM me

I think what you may not be realizing is that specifically, the 525 headers from Merc with a Merc part number is a different quality piece than any other "NON-MERC" CMI part.

Merc told them to make the header cheaper by using less heat treating etc....

In part, this lack of info is what keeps the topic going.

All the other CMI headers are better than the Merc Branded CMI..

Your suggestions regarding the use and taking the time to heat up or cool down is a great idea. Most guys jump out of their diesel truck and slam the door with an 800 degree turbo baking itself to death..

Do you think they will be concerned about a "water cooled" part on a boat?

I'm certainly not defending Merc or CMI, but CMI has told me Merc spec'ed a higher quality stainless than what CMI uses. So who knows what to believe.

i have tested the material on various CMI headers....with a PMI machine including the ones on 525s
Positive Material Identification , it gives you the chemical composition of the material in a % value
CMI uses 304 grade stainless steel quite cheap actually.. but more than adequate
in the 525 application they cut corners on the anealing process/post weld heat treating, by either not doing it at all or not doing it properly and it doesnt help that the work on the headers themslves is probably outsourced out of country where materials and quality control might be questionable
an other possibility is that the welds were not backpurged.....
this causes oxidation of the metal opposite the weld zone and leaches the nickel from the stainless making it super brittle
warming up and down will eliminate 75% of failures and as much as 90%
definitely cost saving measures....304L has the best heat qualities of all the common stainless grades
the metalurgy is actually quite intricate. half a dozen different filler metals can be used.......for specific applications
and a dozen more variables to each each filler metal to be considered

Wow. That's what I thought. :D :D

Now I'm thinking of not even testing my existing 500EFI headers, and just buying new ones. I'm doing a complete rebuild and these are the original CMI headers. Does that sound rediculous or should I see what condition mine are in before buying new?

Stellings +1. If not stellings, i'd go to a stainless marine manifold setup or keith eickert manifolds.

Got enough to worry about with the engines, now you have to warm up and cool down your headers so they dont spring leaks??....F&CK THAT. I'll be damned if im gonna drop 8-10k for some headers and have to worry about that every time i fire my motors up.

NORT
pressure test your existing headers with water NOT AIR no more than 20 PSI using good guages for accuracy for one hr if there is a pressure drop wich can happen because of normalising and heat variables both in water and metal temp bring the pressure up again for an other hr if there is a drop in pressure then you have your answer try to use room temp water to avoid condensation so you dont think the headers are falsely leaking
05/06 CMI headers for 525 were the problem yrs i think those after are less prone to problems
PM me if you have any more ?
THE DISCLAIMER
i am in no way involved with CMI or MERC
just a simple tradesman with a thirst for water and a need for speed!!!!!!!!!

MILD THUNDER
no disrespect mate....but everyone and i mean everyone cuts corners
in my industry customers have an inspector on fabrication site for the last 50% of the project in some applications to make sure that testing and procedures are followed to the letter
if i had a tube bending machine at my disposal i would make my own headers a roached motor because they are paying some poor immigrant substandard wages and pushing for more production with threats
galls me to no end

Why not air?

air in a pressure test is dangerous....... its the volume of air needed at any given pressure
if there is a total failure the volume of air is instantly released
most of the welds i work with in a pressure application are 100% and proven as such by XRAY or ULTRA SOUND and we never exceed 5PSI if we use air
water on the other hand if there is a failure just goes fart!!!!!
much safer
there was an accident in a shop where i worked some yrs ago using air to test a guage failed luckily no one was hurt but we had to cut a pressure vessel in half to repair the damage
uglyyyyy to no end and very very costly........

Do you think CMI uses air to test them? My point was.......since they are so old, even if they tested okay today.......next week they might leak and wreck my new rebuild.

My stellings are 10 years old and they still pressure check perfect and I expect to get quite a few more years out of them.

You get what you pay for, but I also had CMI's from CMI and not merc and they are a better product than the merc units.

if they are that old nort you are probably right.... if you dont run salt... they could potentially last indefinately but i ere on the side of caution.........and a roached motor just plain sucks........

I spoke to Daid at CMI yesterday about testing, he said they use 60 psi air pressure in a tank of water. That's how I did mine. I also used 110 degree water.

60 psi seems a bit high to me but whatever...... and testing in a tank full of water would eliminate some of the danger id lay dollars on dimes that the tank is big
i certainly wouldent be standing beside it at that pressure........not with air anyways........

They won't explode. If anything they would pop a leak with excessive pressure. I used 40 psi to test mine and I agree that it makes more sense to use air. The slightest leak will be visible as a stream of air bubbles, no matter how small. Trying to monitor water pressure changes from a tiny leak seems impossible and trying to keep the jacket pressurized with water while keeping the outside completely dry to watch for wet spots seems very difficult. If CMI uses air pressure then that is how I will continue to test my headers.

Can someone offer insight into what damage could be caused from a leaking header . I understand the potential for hydraulicking a valve , but if the leak was small and caught right away what should i be looking for ?

a leaking header or manifold can be disastrous........cool or cold water touches a hot exhaust valve and the exhaust port on the head instant roached valve,,s or head......worst case senario is a hydraulic-ed bore
usually a roached block to go with the head and valves and on and on if your running wot when it happens cant react fast enough

silly me didnt read all of you post ride

You must be scared to death to stand next to a 150 psi air compressor.

now that's funny!!