4.3L Exhaust Manifold inspection methods / replacement

[kramerpage]

I have two sets of exhaust manifold assemblies. One set that's on the motor that will go into the restored My Rotten Lady and one set that came from the donor boat. I am wondering with both sets from 1989 and both ran in freshwater only. Do I need to be concerned? Is there an inspection method? How long can these last before there is a breach that destroys the motor? Do you just replace them after so many hours. 1500 hours are on the motor now. It runs great and has never given me one issue since 2005 when I purchased her. Thanks for your input.

 

[Buoybill]

Not sure of the 4.3, but with the 5.0, I sealed the ports with plugs and the outlet with silicon. Filled the water jacket with water and let sit for a day. I was looking for a drop in water level or moisture stains in the exhaust chamber. This was done with the exhaust manifold off. I was looking to pressurize it with air and dip it in water, but could not. I made a jig for the intake manifold and checked it.

 

[Bondo]

Is there an inspection method? How long can these last before there is a breach that destroys the motor?

Ayuh,..... Ya pull the riser off the top of the manifold, clean off the junk gasket, rust, 'n crud, then measure the remain' cast iron at the gasket contact points of both pieces,.....

I use a flat file to clean 'em to clean cast iron,....

The manuals show the limits,....

'n of course, ya need new gaskets, I use the Merc carbon composite gaskets, on dry,....

In sweetwater, they rarely rot out, but I won't say it never happens,...

In the brine, yer lookin' at 'bout 5 seasons,....