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496 Mag - 360 hrs - time for manifolds?

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Old 04-15-2011, 01:31 AM
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Default 496 Mag - 360 hrs - time for manifolds?

Hey All
My Cobalt 255 has 5 seasons and 360 hours on it. The last 3 seasons running in the salt.

At this stage, is it even worth having the manifolds and heat exchanger boiled and inspected or do you just replace the parts now?

Is it worth buying OEM or is this a legitimate opportunity to buy on a reliable after market product that ups the HP without sacrificing reliability or fuel consumption too much?

thanks in advance for the opinions.
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Old 04-15-2011, 07:50 AM
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GLM makes a nice OEM replacment manifold.



http://www.boatstoreonline.com/glmexhaust.html
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Old 04-15-2011, 08:01 AM
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I'd take the risers off and take a look.
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Old 04-15-2011, 08:11 AM
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We sell the heat exchangers (USA only) and manifolds (both Chinese and American made) for that engine if you need help with new. But Dave M is right...pop off the risers and take a look. If the manifolds look good you're probably ok. The heat exchangers are harder to evaluate. If 4 years old in BC, you can probably clean, properly test both circuits and be fine. Just know you're going to release crud into your glycol circut...no real way to stop it.

If you were in South FL, I'd have a different opinion. But up there....prob ok.
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Old 04-15-2011, 10:27 AM
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I have a pair off takeoff's . Call me I'll make you a great deal on them. They came off a new boat .

Tim
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Old 04-15-2011, 10:32 AM
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Quote:
Originally Posted by glassdave View Post
GLM makes a nice OEM replacment manifold.



http://www.boatstoreonline.com/glmexhaust.html
GLM for the 496...not yet. GLM makes a good looking product however I have seen so many failures out of the box that I would never trust them. Its not worth it. GLM = China crap.
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Old 04-15-2011, 10:33 AM
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Quote:
Originally Posted by Fivefasts View Post
Hey All
My Cobalt 255 has 5 seasons and 360 hours on it. The last 3 seasons running in the salt.

At this stage, is it even worth having the manifolds and heat exchanger boiled and inspected or do you just replace the parts now?

Is it worth buying OEM or is this a legitimate opportunity to buy on a reliable after market product that ups the HP without sacrificing reliability or fuel consumption too much?

thanks in advance for the opinions.
You should just replace with new ones...and send me your old ones
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Old 04-15-2011, 11:54 AM
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The early model 496 engine from Mercruiser years 2000thru 2004 had aluminum base manifolds and in salt water use they will corrode thru faster than the new iron units that Mercruiser has been using on the 2004-1/2 thru current 496 year engines. There are usually quite a few late low hour used sites here on OSO and on ebay for sale that can be purchased for a lot less than new from Mercury. I would recommend using the newer iron manifolds as they will last longer in salt water and you should also consider a flush fitting on the engines to make sure you are flushing the entire system after use with fresh water to slow down the salt buildup and corrosion that occurs in all salt water exhaust systems.

Best Regards,
Ray @ Raylar
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Old 04-15-2011, 03:03 PM
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thanks everybody

I thought (was hoping) you would all be more insistent to use this opportunity to add some performance (its easier to convince the wife if i am replacing something that needs replacing!) manifolds. From what i read, the manifolds are the least expensive way to add a little HP. I figured if i have to replace them anyway... : )

Does the serial number of the motor confirm its mfg date?

Its a 2005 Cobalt 255, but maybe the motor was built in 2004?
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Old 04-15-2011, 04:37 PM
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Quote:
Originally Posted by Westcoast View Post
GLM for the 496...not yet. GLM makes a good looking product however I have seen so many failures out of the box that I would never trust them. Its not worth it. GLM = China crap.
Point taken, i hadnt heard of issues. I have several friends that have used the small block sets with no problems. Thanks for the info, I'll hafta look into it further.
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