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Old 01-22-2007, 06:08 PM
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Default CMI Headers

I'm on the second of two sets of CMI headers on Merc 525's that leaked badly. First set after 100 hrs, second after 170hrs. This time hydro locked a piston and damage internally.

How many others have had this problem?

Thanks,

Mark
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Old 01-22-2007, 09:28 PM
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Default Re: CMI Headers

Stellings has a new 525 header available.

Last edited by Too Old; 10-24-2007 at 12:13 PM.
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Old 01-23-2007, 02:41 AM
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Default Re: CMI Headers

Eventually everybody!
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Old 01-23-2007, 07:35 AM
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Default Re: CMI Headers

Originally Posted by Donzi502 View Post
Eventually everybody!
Sounds like you have personal experience here. I've been told to drain the headers sfter each use. This will save motor from major damage but issue of headers leaking still remains. This is my first boat with headers, is this something I will have to deal with on a regular basis?
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Old 01-23-2007, 07:37 AM
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Default Re: CMI Headers

Is you boat a staggered set up? Is the problem with the forward motor? If so you need to get the header supports. A buddies 39 Cig with 525's had cracking issues too. (forward motor)When this happens, water gets in the oil, the contaminated oil packs up the oil filter. With the oil filter packed up, the oil cooler is bypassed and oil temps go to the moon.

Last edited by Biggus; 01-23-2007 at 07:42 AM.
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Old 01-23-2007, 08:24 AM
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Default Re: CMI Headers

Originally Posted by Biggus View Post
Is you boat a staggered set up? Is the problem with the forward motor? If so you need to get the header supports. A buddies 39 Cig with 525's had cracking issues too. (forward motor)When this happens, water gets in the oil, the contaminated oil packs up the oil filter. With the oil filter packed up, the oil cooler is bypassed and oil temps go to the moon.
Thanks for the info, I had the exact thing happen to the staggered motor last spring with the exact same symptoms. I have not installed the support brackets on the staggered motors. The one that I am having problems with now is the rear motor installation which is a standard CMI header. DO you have any pics of the header supports?
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Old 01-23-2007, 04:26 PM
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Default Re: CMI Headers

Originally Posted by MarkDonzi View Post
DO you have any pics of the header supports?

Sorry, I do not have pics. He has since sold the boat.
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Old 01-25-2007, 08:53 PM
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Default Re: CMI Headers

Are these headers flexing that much? This is the first time I've heard of problems with cmi's
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Old 01-26-2007, 02:25 AM
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Default Re: CMI Headers

I have had personal experience. I treat my headers as if they are leaking weather they are or not. I have taps with long extensions and drain them every time i turn the engine off and fire with the taps open for a couple seconds to blow out any moisture. I have a very small bilge pump to suck the water out. Its all worth it for the bling and weight and HP. Thats on my Donzi 454 Mag. In the race boat in my signature picture we have stellings. Same deal but no builge pump cos we dont park up and have lots of starts between trailer. Jas
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Old 01-26-2007, 06:49 AM
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Default Re: CMI Headers

I've talked to a few people that do exactly what you do.It sounds like eventually these headers are going to leak. Have you ever used your drainage points to pump up the headers with air to check for leaks? I think by removing and plugging a couple of hoses it ccan be done right on the motor. I like your idea of a small second bilge pump, I'm going to check on that also. Thanks for the info!
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