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heavy rust in fwc manifolds....

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firepiper

Contributing Member
While changing my exhaust elbows this weekend, I noticed some pretty heavy rust in the exhaust gas passage of the manifold. The sealing/gasket surface was/ is fine. This setup has the ss blockoff plates at this location. These manifolds,fwc, are five years old. So, I chipped what I could and cleaned the rest with a dremel and sanding drum. I looked, inside with a light and mirror, it appears only to be at the end...about two inchs in. Any thoughts? Thanks, Mark
 
Run in fresh or salt water; and how long has it been run in either? That's the question you must answer. (About 10 to 15 years in fresh water, and 5 in salt water.)

What you don't want is for water to leak into the motor from a leak and, if you're not paying attention, starting the motor up! Be extra careful for the next few starts, especially ver night after a run. Listen to the starter and, if it hesitates, STOP and pull plugs until you locate the cylinder with water in it.

Jeff

PS: RRRRRRRRR is fine; RRR--hesitate--RRRR is not.
 
Some rust in the exhaust passage is expected...those gases are extremely corrosive. Like Jeff said, you don't want water to enter & accumulate in the manifold. Hopefully, the new elbows will resolve this issue.

The best indicator i've found for determining if the source is an internal leak in the elbow/riser is to look at the rust pattern. If it exists (heavy) at the bottom of the gas passage and has an even extent up both sides, it is likely to be due to residual cooling water. If it is spread uniformly around the gas passage, it is likely due to the environment.

BTW, the more you use the engine (not just idling at the dock), the less rust damage to the exhaust system....nowadays, that needs to be balanced with fuel costs.
 
somehow my reply got lost. The boat is in salt, on a mooring and used often, charter and family boat. I found the rust to be at the aft end of the manifold from the elbow edge in about two inches. The gaskets and block offs looked good. I put new ss block offs on anyway. Always starts fine, and no water in cylinders. hmmm
 
Recheck that elbow/riser torque after you run it. It will loosen and manytimes dribble a bit of coolant into the exhaust.
 
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