What is the average lifespan for Mercruiser exhaust elbows and manifolds?

Question

I have a 2003 Mercruiser 350 Mag MPI that I run in salt water. The engine has around 150 hours. I'm trying to determine when I will need to replace the elbows and / or the manifold.

Answer 1

For a 2003 running it in salt water, you're doing very well...I'm assuming you flush it out after use because they're lasting as long as they are. You should expect, with regular fresh-water flushing, a good 5 to 8 years of use out of them because you have low hours as well. Depending on the amount of use and where engines are run, that number will be different. You can inspect them by removing the exhaust boot that runs from the elbow to the Y-pipe and looking into the elbow with a flashlight or something. You can also start the engine and let it warm up, then feel the temperature of the elbows and manifolds. If they're somewhat lukewarm (you can touch them for a few seconds) then they're OK, but if one side is particularly warmer than the other one, or they're really warm/hot, then you might want to replace them because the water isn't getting circulated. You'll want to do that while it's running, obviously, so that the water doesn't sit in there and get hot.

Answer 2

I am going to echo Mark, about five to seven years with proper maintenance and flushing.

Answer 3

There is no average under your conditions. However, it's not that hard to inspect.  Remove the hose clamps and pull the hose off.  Use a light and mirror. If necessary unbolt and inspect.  Replace the gaskets before remounting.  From past experiance I've seen them fail in five years, but more often ,ten or more years.  A lot failures are caused by poor  off-season storage.  Hours of use is not a factor, just salt water and age.  In fact more use is better.