525 Header Leak
 

I am about to switch my stock CMI headers to Stellings, but I want to be sure I understand the problem with the CMI headers leaking before I order the Stellings. Right now I am not having any problems with the headers and everything is working perfectly, but I am looking at this swap simply as a preventative or precautionary measure.

From what I understand, the problem with the CMI headers is a design flaw and a issue with the thickness of the water jacket that causes them to leak with age. Am I correct in my understanding that the Stellings headers do not have this problem? If I change to the Stellings headers, will I have to worry about this potential problem any longer?

Oh yea, the engines are Merc 525EFIs with 200 hours.

As always, thanks for the help.

It is my understanding that CMI built some of the headers for the Merc 525's to a weak spec. Is it practical for CMI to rework/upgrade these headers in a way that give these headers extended life?

Thanks for the link. It says quite a bit about the CMI headers leaking, but there is only one mention of replacing them with Stellings. Is anybody running the Stellings headers. Will they have the same problem?

Talk to Old School, he has Stellings on his, I think they are 5-6 years old. My buddy went through 6 sets of CMI's and now a set of big tubes on his new (used) boat have a leak (80 hours), he is ordering Stellings.

IMHO, CMI, Stellings etc. are stainless and after some time they will all leak.

The new CMI's are anealed (heat treated) which might help but good luck in whatever you do!

Here is what I've been told: The 525efi heads are "specific" bolt pattern only for the header bolt pattern. Therefore, ONLY the Mercury Racing dealer CMI headers will fit the bolt pattern. CMI can't even sell you a set directly. Stellings I hear won't bolt up. Kind of like Microsoft cornering the market right? Just what I've been told. Don't shoot the messenger.

no problem , i'd go eickert or sm...

thought heads are edelbrock?

I am not sure how they work but I am having drains put in mine so when they sit the water doesn't pool @ the block.

Are the headers on the 525,700,850,ect the same? Same problems? Just fewer out there? Doug

No the 525 CMI do have a special bolt pattern, but I heard Stellings now has the proper pattern for it.

Will,
Give Randy at Stellings Marine a call (559) 485-9394 and he can assist you with any question and needs ... real good guy :cool:

Chris

What we have been doing as a preventive on CMIs is putting in By Pass self drains on the headers so the water drains out the transom of the boat. so far this has been working well, the biggest problem is the water is laying in the header and not going anywhere.

the water sitting in the ports or water spaying on your red hot exhaust valves from a leak are death to your engine....

check for leaks and check them often.

swim at your own risk...

This is what a diagram would look like

Is this stictly a saltwater problem? Steve

I don't know if freshwater would have the same result but water laying in a Stainless Header is never good. So to get it out is the best way of not having a future problem.

My experience including antifreeze over numerous winters, says this need to drain might/must be related to the salt.

Thanks for the input. For now we have been draining them after flushing just to be sure. Stellings does make a direct replacement. I'll call them to see what they have to say, but I wanted to hear it from you guys first. Not that the folks at Stellings would do this, but I would rather have opinions from people with first hand experiece than from a salesman trying to sell me something. Thanks again for all of the responses.

http://www.stellingsmarineproducts.c...roducts_id=155

For what it is worth I had my headers crack and leak at 260 hours of mainly fresh water use. I was seeing water drops on the oil fill cap. I read tons on here about them getting corroded and leaking and cracks too. My cracks were at the top where the four tubes enter the collector area. I had them repaired locally. The shop removed all of the original welds material and re-welded with 321 stainless rods which have higher nickel content then the 316 which CMI uses. The increased nickel allows for better expansion and contraction.....time will tell. I used a bore scope to inspect the water galley area and found NO CORROISION at all....again mainly fresh water but never drained. Also like many on this site only my forward engine pipes cracked possibly suggesting vibration and fatigue. My rear engine is fine.

I made a very simple, fast, and inexpensive pressure test kit so I can check the pipes in the future. It takes about 10 minutes per engine. Maybe a test kit would set your mind at ease and save money too. I agree with the folks on here...headers will fail it's just a matter of when.

525 header failure
 

hey Frank ,it's Joe Amoroso.....I've been reading the posts on here,and man i am having issues with CMI.I'm at the point of getting in touch with boat publications,and maybe even litigating.I had a new starboard side starboard header,and 2 neew exhausts put on a month and a half ago.I noticed an exterior leak 2 weaks ago.Upon further evaluation,noticed that where the exterior leak was,(near i believe the coupler?)there was a missing weld.My mechanic informed me,that the new setup leaked into the 6&8 cylinder.Now i have to have this replaced,as well checking the other side (port engine)the port side header is leaking on this side as well.Last June sent all 4 exhausts back to Cmi to have them pressure tested and rewelded.This was because of damage that occured to my # 6-8 valve on my port engine.All Cmi does is give you run around bull****!!!

This problem seems to be happening on CMI to Mercury set ups 525s and 700s.
Nor-Tech started putting in By-Pass drains in the CMIs and it seems to help, we have installed them in a few 525s and now we are doing it in a 700 that just had a CMI failure, had the headers rewelded.

I run antifreeze in mine,

I feel for you that stinks:mad: man, I have had my stainless marine for 14 years gen 2 dry they don't look as nice as the stellings or cmi but made as much hp. now with the gen 3 with 4 1/2'' tails your exhaust flows better, try looking them up my bud had to have his Etop cmi head fixed after 3 or 4 seasons:rolleyes:. so look at SM.

I took my Stellings off because of continuos leaks, replaced with SM Gen III and haven't had any more problems and make more power.

eikerts are the way to go, IMO.
Dean

Nice!:ernaehrung004:

I had the Gen III's in my hands and was ready to make more power over my E-tops, I couldn't wait, then found out the hard way that my centerlines are too tight.. The Gen III's require at least a 33-34" crankshaft centerline, I was at 32". They even sent me a pair of machined manifolds, still no luck... I can honestly say they are a GREAT piece and the ports are huge, no wonder they do so well on blower motors.

I wound up going with the Gen II system and we made the tails 95% dry and did a 4" to 4 1/2" step up in pipe size. I did not notice any power difference between my etops and the SM II"s... The SM III"s would have made more power.

I had the Gen II's on my last boat and they were over 10 years old and performed wonderfully. I have no reason to expect any less out of my new system! :cool:

One thing to keep in mind. When the salt water leaks into the exaust cavity, it lays on the bottom of the header gasket, and begins to eat it's way through the aluminum Cylinder head. Which in that exaust area is less than a 16th of an inch thick. I have a pile of junk 525 heads. Pay close attention, to your headers, those heads are not cheap, as they are Mercury only parts. Smitty

What a mess.....

But, Trione should be able to fix those heads, no?

Some of them. But you would not believe how thin the casting is.

We have two fairly new triple engine boats at our marina, one with 600's, the other with 525's. Both of them have already been thru all 6 sets of headers and tailpipes. The one boat had to have it's heads rebuilt because they didnt' catch it in time and the boat sat over the winter and all the valve springs broke from surface rust. They had the headers fixed last year and decided to buy new sets over the winter.... Another problem they had was with the tailpipes, at the flange the SS eroded away to nothing. The headers are quite expensive but those center engine headers sure do cost a chit load of cash.... :(

I sure am glad I decided NOT to buy CMI's again. but I haven't been a big fan of them for a long time anyway.. ;)

If you have a bad set of heads on a 525, what would be a good aftermarket replacement? If your buying a set of headers you could then go to a standard bolt pattern. Has anybody done this? Doug