exhaust manifolds

E

edsmax

Member
Feb 11, 2009
182
Greenwich Bay, RI
Boat Info
2002 Sundancer 240
Engines
357 Mercruiser MAG 4V 325HP, Bravo III
WHat is the average life of Mercruiser exhaust manifolds when subjected to salt water? My 240DA is a 2002 model year and I am not too sure what to do. I dont even know if my existing manifolds are original (they have a bit of surface rust so I suspect they are). Any ID numbers stamped on them that would indicate their age? Advice?
Ed
 
It has been my experience that after about 5 years you need to start looking for issues. I did my father in laws 1999 boat in 2005 (new mainfolds and elbows) and one side was showing clear signs of leaking. I think you are really pushing it with a 2002 with original components.
 
I have the same questions... I have original exhaust on my 2001 190... I know i need to change them... My '01 340 looks like the second set, but I am not sure... I plan on pulling of the one side this week end, when pull my generator out, and I will inspect the manifold, riser, and elbow... I installed a Jet Ski lift and plan also to pull my generator. If my exhausts are shot, I will assume my raw water impellors are shot too, and I will replace them too.... I am glad I don't live in Florida because I would have no time to do maintenance... :)
 
I just replaced all of it on my engines. I don't know the original schedule of replacement but know they had been replaced at least once before I got them. The 4.3's originally came with one piece manifolds/risers and when I got the boat it already had the 2 piece conversion performed. The boat has been in salt water for the entire 13 years - slipped for the first 11 and now trailered since I've owned it for the last 2 years.

The exhaust I took off was in bad shape - rust crumbles, thin walls on the risers and the gaskets were definitely in need of replacement. I will now be inspecting these every year now that I have new components and will replace the exhaust and riser gaskets every year since the parts are cheap and easily torn. If you have original components on a 7/8 year old boat it is almost definitely time to replace - but it's easy enough to remove and inspect.
 
Time to change them..

I just replaced mine. Do-it yourself project. On the outside they look great, but once removed, lots of rust crumbs and a very small leak had developed to the block..

Needless to say, this is the number cause of engine failure.

good luck..
 
Ok, so now I am convinced to change my manifolds in the spring. I have found kits out there that have a pair of manifolds, a pair of elbows, and all gaskets....but, ,y setup has what I believe is called a 3 inch riser between the manifold and the elbows. Does any vendor sell the riser as a kit with the manifolds and elbows??

I have a pic of my setup but need to figure out how to post it.
Ed
 
Ok, see attachment of my manifold setup. Might be able to see a little rust on the outside.
 

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I have not found them as a complete kit... I intend on ordering the manifold assembly, risor assembly, elbows and gaskits...
 
AH, the plot thickens; I just emailed the company I bought the boat off of and asked for a service history. Unfortunately, they only had the history from 2007. Here was his response:
"sep 07 - new oil and filters
-sep 08 - " "
-sep 08 - new injectors, gimbal bearing, new gaskets for risers manifolds,
heads, as well as a valve job"

So, it had all of the exhaust gaskets changed, but not exhaust itself? And what is a valve job and is it related to a leaking exhaust problem. Glad they changed the gimbal bearing...

Ed
 
And what is a valve job
Click to expand...

Removal of the heads and regrinding the the valves and seats, perhaps repairing guides. Common procedure. it wouldn't have anything to do with your exhaust manifolds.
 
edsmax said:
Ok, see attachment of my manifold setup. Might be able to see a little rust on the outside.
Click to expand...

See that white line between the riser and the base of the elbow? That's salt residue leeching out. The gasket is letting water past. The heat evaporates the water and what's left is the salt. Salt water getting outside the riser probably means salt water getting by INSIDE as well. Even if the risers and elbows are good the salt corrodes the machined surfaces making even a new gasket risky.
Time to replace.
 
jg300da said:
See that white line between the riser and the base of the elbow? That's salt residue leeching out. The gasket is letting water past. The heat evaporates the water and what's left is the salt. Salt water getting outside the riser probably means salt water getting by INSIDE as well. Even if the risers and elbows are good the salt corrodes the machined surfaces making even a new gasket risky.
Time to replace.
Click to expand...

This was happening to mine as well. Well - that and a water leak I happened to notice when flushing the engines... :smt021

The poor condition of the mating surfaces along with the rust flakes prompted me to replace everything on both engines. Not worth the risk to just try and do new gaskets unless your manifolds and risers are in great condition.
 
Trust me when I say....DON'T skimp out on the riser/manifold replacement as I am about to place an order for a long block on the port side (not covered as a wear item). Overall, about $16K. Much cheaper to change the exhaust before the water pitts your cylinder walls.
 
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