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7.4 mercruiser: hole in The intake manifold

P

pietro

Contributing Member
Hi all
see the pic below? Is a 7.4 1989 with some rust, corrosion and a hole you can see just right of the bolt. The boat is out in my warehouse, I head it for free. The engine stata and runs regularly, but I cannot have it in the water so there is no charge. I am replacing the part, but how can the engine runs despite of this hole? Maybe it is not involving the intake duct?
imagejpeg
 
theres no pic. but you cant have a hole in the intake manifold and not have exaust leaking or water entering the oil
 
Sorry for the pic, I can't attach it from the iPhone. Anyway, you mean that the corrosion doesn't involve the duct and the engine is able to run even. But I would better replace the manifold with a brand new one. On the other engine I can see a welded zone more or less in the same position: maybe the former owner decided to weld a crack instead of replacing the whole part. By the way, I found the manifold on several web sites, part number 59974, 499$
 
that area is part of the exaust crossover to supply hot gas to the area marked as B. that heats a bi-metallic element to open the choke plate on the carb.
A and B are not repairable ,replacement is the only option.When you recieve the new intake manifold gaskets there will be a thin metal plate with a small hole to restrict the gas, they fit in the gasket,
 
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