How do you know when it's time to change risers and manifolds

MRWood

MRWood

Well-Known Member
I have a Volvo Penta 4.3L v6 inboard motor. I'm suspecting it might be time to change the risers and manifolds. The last time they were replaced was Jan 2012. Last season and this season when draining the exhaust manifold there was plenty of metal scale that came out with the water. I had to keep poking my finger in the drain hole to keep getting the scale pieces out. I pulled the port side, just to inspect, they look OK but not pristine by any means. Here are a couple pics. Any advise is greatly appreciated.

IMG_3537.JPG IMG_3538.JPG
 
Those still look fairly good. When your mind keeps drifting onto your manifolds soundness its time. Keep an eye on your engine temp if it starts to run hotter your likely plugged up. Murphy's Law will dictate that they fail at the worst possible time so replace before then.
 
Terrin....yeah I've seen little bumps up in temperature on the gauge. I was thinking it was the gauge getting faulty as I'd tap it and it would come down. I was also thinking it was starting to run a little hotter that it should. Was running 170 and a bit higher at times. I'm thinking that's a bit hot?
 
170's just right imo...
 
Take them to a rad shop and have them boiled out, cleans them right up. If you trailer your boat and flush your motors you are going to get a lot more time out of them then someone that moors their boat all the time. Yours still look pretty good, probably still have some life left in them
 
My offshore going buddy changed his every year or two. He also filled them with coolant in the winter, and sometimes glass beaded them out in a blaster. By his thinking 2012’s would be toast.
 
Tugcapitan said:
My offshore going buddy changed his every year or two. He also filled them with coolant in the winter, and sometimes glass beaded them out in a blaster. By his thinking 2012’s would be toast.
Click to expand...
He'd be into his 3rd set by now. It's probably a good idea to change them rather than try get some extra time out of them.
 
bigdogeh said:
170's just right imo...
Click to expand...
I think it's been heating a little as I've been seeing some coolant in the bilge. I believe the coolant tank has overflowed when things got a bit hot. This all leads me to believe that the risers are getting partially plugged and then heating more than it should
 
I would change them out. You've got decent life out of them. Why risk it, for what.... another year? If it's getting thin inside and the raw water transfers between the coolant side to the exhaust side well you know what happens then! Hello new motor!
I've been told 5 years in time they should be changed even if it is low hours on them.
This goes back to the maintenance thing. You can never do too much maintenance to a boat. It may seem like overkill but when you have peace of mind knowing that things are good (or should be) it's one less thing you have to worry about.
 
may be a good time to replace the thermostat as well...
 
If it's just your risers their easy and cheap to replace,it's time.Are your manifolds FW cooled? They are pricier to replace.Shop around for best priceing.
 
Thanks Rayvon. The manifolds are not FW cooled. They use the same raw water that flows through the risers.
 
spend a bit more and get the KEM Kodiak alloy headers and risers save a fair chunk of weight and FWC system
if your totally raw water cooled ....

iam running a 4.3 l FWC KEM kodiak with 4bb converted to merc and gen 2 leg ...
 
and if your stuck like me with the 4.3 size look at there KEM website there doing the new alloy4.3 block
kicks out more than a V8 350 but its in the same price range as a big 4 stroke
 
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