Re: Mercruiser 470 (170hp - 1986) - Exhaust Manifold Erosion
The OLE outta here.
I believe you should be fine. Only exhaust travels through the area. The area to be concerned about is the water jackets and the exhaust chambers. Looks like yours is starting to corrode also. In your picture, the left arrow almost points at the corrosion if you continue the arrow. That exhaust chamber is for #3&4. . I had an exhaust manifold corrode in between the 2 and water was going through #4 cylinder and getting into the intake manifold. # 4 cylinder would not fire at low RPM's . New exhaust manifold fixed the problem, luckily I had another one.
"GET'EM OFF THE BOTTOM"