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Noel Schembri
Noel Schembri, Marine Technician
Category: Boat
Satisfied Customers: 1951
Experience:  Advanced technical diploma
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I have a 7.4l / 454 Mercruiser engine. The exhaust manifold

Customer Question

I have a 7.4l / 454 Mercruiser engine. The exhaust manifold got cracked at one of the bolts. Now I need to replace. This is a two part question 1) Do I need to replace Both Manifold Exhaust and can It be with aluminum Exhaust Manifolds. 2) Do I need to replace them both or just the broken one, and can they be mismatched (one aluminum and cast iron). Any help is appreciated
Thanks, ***@******.***
Submitted: 1 year ago.
Category: Boat
Expert:  Noel Schembri replied 1 year ago.
Hello my name is ***** ***** I will assist you. First thing it depends wether the manifold got cracked due to wear and tear or due to over tightening. If due to wear and tear and the manifolds have been installed for more then 4-5 years i suggest you replace both manifolds as the other is due to fail soon. As for the aluminium, if you are using it in fresh water you can use aluminium ones but in salt water no you would need to use either cast iron or stainless steel ones. As for the mismatch i do not suggest you do that as it will effect the performace from one side to the other of the engine. So either use both cast iron or both aluminium. If you have further questions let me know. Noel