Changing manifold on a 2004 3.0.

[charliedaubitz1]

The drain line on my exhaust is plugged. I removed the manifold and have ordered a new one. The line I think is a bypass line that runs from the coldwater supply line coming through the transom from the impeller to the t is where the manifold drain is looks like it pumps cold water into the manifold jacket, Is that line to help keep the riser cool till the block fills and starts circulation. I'm replacing both the riser and the manifold. The riser was cracked on the outside and staining the manifold, no leaks inside. I have overheating even when the stat is out, new impeller and lots of water pressure from the impeller. does the circulation pump ever go out without making bearing noise, turns fine. I'm changing the manifold and riser because I think it's restricting the water flow, I'll soon see, parts will be here Monday or so.

My new manifold just came in. the exhaust port is large and rectangle, the merc cruiser gasket that came with it isn't the same size and has a vertical gasket in the middle of the port with no surface for it to mate against it, do I trim the gasket to match the port?

 

[matt167]

Did you order the correct gasket? Cylinder heads changed around 1990 and went to large ports. Your 2004 should have large ports and your manifold sounds correct but perhaps the gasket is for an older motor. The bolt pattern is the same

 

[charliedaubitz1]

Did you order the correct gasket? Cylinder heads changed around 1990 and went to large ports. Your 2004 should have large ports and your manifold sounds correct but perhaps the gasket is for an older motor. The bolt pattern is the same

the gasket came with the manifold: https://www.amazon.com/dp/B002IQYGEU?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[cyclops222]

Amazon and the WEB for marine parts ? Oh well

 

[charliedaubitz1]

Amazon and the WEB for marine parts ? Oh well

Sorry, the weight and shipping made the difference. Prime.

 

[charliedaubitz1]

Sorry, the weight and shipping made the difference. Prime.

On a side note, I use West Marine in Tampa near Tyron Mall when I can if they have the part. when I tried on this site at checkout to discover shipping charges I received this error message:

"An error has happened during application run. See exception log for details.
Could not write error message to log. Please use developer mode to see the message."

 

[charliedaubitz1]

on the manifold gasket supplied with the 860235011 Mercury Marine kit, the gasket doesn't fit the ports. if you don't cut out the gasket in the center, it will flap in the exhaust and remove itself weaking the gasket and eventually causing an exhaust leak. Also the manifold kit is missing a 3/4 plug, the old manifold has one but it's a 5/8 allen wrench to remove it. You would think Mercury could have the correct gaskets made and supply that plug.

 

[charliedaubitz1]

Another caveat when changing this manifold on a 3.0. On the side of the manifold close to the stud on the carb base there is a drilled and tapped hole that leads into under the carb intake runner, if it's left unplugged, it's a vacuum leak. It causes a uncontrollable idle and dieseling when shutting off. I have a picture but my inability to post pictures here continues to flummox me.

 

[charliedaubitz1]

Another caveat when changing this manifold on a 3.0. On the side of the manifold close to the stud on the carb base there is a drilled and tapped hole that leads into under the carb intake runner, if it's left unplugged, it's a vacuum leak. It causes a uncontrollable idle and dieseling when shutting off. I have a picture but my inability to post pictures here continues to flummox me.

x.com

x.com

Where there's a will. there's a way

 

[Scott06]

Another caveat when changing this manifold on a 3.0. On the side of the manifold close to the stud on the carb base there is a drilled and tapped hole that leads into under the carb intake runner, if it's left unplugged, it's a vacuum leak. It causes a uncontrollable idle and dieseling when shutting off. I have a picture but my inability to post pictures here continues to flummox me.

No one can currently post pictures so don’t take it personally. I think that hole maybe for pet of the throttle linkage on older models it sure it should go through to intake passage. Is this an oem or aftermarket manifold ?

 

[charliedaubitz1]

No one can currently post pictures so don’t take it personally. I think that hole maybe for pet of the throttle linkage on older models it sure it should go through to intake passage. Is this an oem or aftermarket manifold ?

Mercury made it for this application so it's OEM, the manifold I removed had no hole there. https://powerboatsupply.com/uncateg...-mercury-exhaust-manifold-assembly-860235a04/

 

[Pmt133]

The replacement I had also had a hole there. Seems it is built to work for both applications. Sealant and an appropriate sized bolt fixed that problem for the 11 years I ran it.

 

[charliedaubitz1]

Mercury made it for this application so it's OEM, the manifold I removed had no hole there. https://powerboatsupply.com/uncateg...-mercury-exhaust-manifold-assembly-860235a04/

The replacement I had also had a hole there. Seems it is built to work for both applications. Sealant and an appropriate sized bolt fixed that problem for the 11 years I ran it.

It fixed mine as well, I only posted about it so others would know and not find it accidentally like I did