4.3 Lx v-6 uneven heat exhaust manifolds?

[Sparks27]

New to me 97' regal 18'. 2nd time out I notice the starboard side manifold is warmer than port side while cruising.
I've read that the risers should be replaced every 5-7 years?
The risers and exhaust manifolds look to be one piece on this engine #0K012008 when do you know to replace?
This boat is fresh water only as far as I know (previous owner stated)
Can I flush these? Don't see any removable plugs?
Thanks, Sparks

 

[JoLin]

Starboard side elbow/riser always runs warmer than the port side on a GM v-engine. Question is, can you hold your hand on the warmer riser for 10 seconds without discomfort? If you can you're likely okay. The 5-7 year replacement guideline is for motors run in salt (like mine).

My .02

 

[Sparks27]

JoLin,
I can keep my hand on there no problem, the port side runs pretty cool.
I'm sure these manifolds are OEM 20yrs old.
I will use a temp gun next time I'm out.
Thanks, sparks

 

[Bondo]

The risers and exhaust manifolds look to be one piece on this engine

Ayuh,.... If you've got the 1 pc. "Batwing" manifolds, get Rid of 'em,....

There were problems with the cores shiftin' in the castin' process that leads to catastrophic failures,....
I seen it happen 3 times myself, once with OMC castin's, 'n twice with Merc castin's,....
Find the conversion kit to 2 pc. manifolds, 'n risers,...