4.3l mercruiser exhaust, valid test?

[riverratjody]

I read the tech info on testing exhaust manifolds, but I have the one piece "batwing" manifolds. 1998 4.3L Mercruiser. Never been in salt water. I have gotten water in the cylinders twice. The first time was after it dieseled really bad (both sides had water), and the second time was after I had to go at idle speed for a long time (only one side this time). So I pulled the manifold to check it. Please take a look at the below photos. I filled up the exhaust cavity, not the water cavity and noted that it went down about an inch in 20 minutes, as shown in the photo. In a few hours it had dropped lower. Is this a valid test since I had to use the exhaust cavity instead of the water cavity? Do I need new exhaust manifolds? If so, do I go with the cast iron, or the aluminum? I also found that the shutters were gone and plan to replace them. Thanks for any help. Jody

 

[Bondo]

Re: 4.3l mercruiser exhaust, valid test?

Do I need new exhaust manifolds?

Yes...

 

[180shabah]

Re: 4.3l mercruiser exhaust, valid test?

Yes you need new manifolds - stick with iron, and look for a 2 piece manifold conversion kit.

Next replace your raw water impeller, and never neglect it. It probably caused the overheat that took out your manfolds and water shutters.

 

[riverratjody]

Re: 4.3l mercruiser exhaust, valid test?

Thank you both -especially about sticking with iron, as I did not know which to buy.

 

[dsmmace]

Re: 4.3l mercruiser exhaust, valid test?

I like the look of the IMCO thumper V6 manifolds, but I have not heard of any back to back comparisions.