We have a 292 with 6.2L's. The manifolds and risers were replaced in 2009. We have some very minimal surface rust on the joint between the riser and manifold. Is this a common occurence? We run in salt water but come back through fresh water (river) to flush them out. Should we be concerned? Maybe pull one to inspect it?

Pulling a riser for inspection is a good idea. May just need new gaskets, but you want to make sure they arent rotted.

Mine started doing that about a year before the riser went. The gasket you have very rarely goes bad, you may have a riser with a very small pin hole and the water is running down and acumulating on the lip, then working its way through the gasket. Pull the worst one and look inside the riser there should be no rust it there if there is its bad. From what I have seen 4 years is about all you will get out of the "dry" gasket riser.And the gasket is around 50 bucks.One of the reasons I did not put Mercury back on when mine went.

hmmm...i am going to pull the worst looking riser tonight. i will post pictures. The joint between the riser and manifold is unprotected (no paint) right? So some minimal rusting at the joint doesnt sound that uncommon.

Its possible that there is nothing wrong with it. Stinks to waste 50 bucks on a gasket, but better than worring about it all summer or sucking water in the cylinders.

If its bad you may not beable to get the riser to seal back to the manifold. A machine shop should beable to surface the mating areas to give a good seal. Or you can get a thick flat piece of tempered plate glass and use it as a sand paper holder and surface the cast iron your self. Plate glass is as flat of an item as you can get off the shelf. You will bevel the edges using a file.

LC

Was thinking, these gaskets almost never leak the riser will rot out first. So before you pull one loosen up the exhaust clamps and slide the rubber joints out of the way. If you (carefully) stick a small screwdriver in between the rubber and the Y-pipe and spray some silicone its easier. Look inside the riser on the inside part there should be no rust, if there is then further inspection is needed but if not just keep an eye on it.

That is very common, the bare surface rusts, sometimes it may weep a bit until the manifold warms up slightly, happens with multi layer steel head gaskets also

took one off last night...so the rust at the joint had me a lot more concerned than I should have been. The mating surface looks great. Only the outside visible edges are rusted which is odd. Anyways there is some rusting going on but only surface rust. Everything is solid and no evidence of leak thru. I'm gonna clean all of them up and re install. I'll post pics later if I can.