What to inspect when replacing Risers/Manifolds

RussWalters

Seaman Apprentice
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Jun 25, 2018
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34
I will be replacing my Risers/Manifolds shortly on my VP 5.0 GL-E. My question is, is there anything in particular I should be inspecting as part of this process to see if anything else is going on? On my Starboard riser, there is definitely some rust streaks on the outside that makes me believe there is some leaking going on, and that riser is much hotter than the port one. I'm wanting to make sure there is not other serious damage that has been cause in the head unit.

Engine is running fine, although has some issues cold starting sometimes and idles a little rough when first warming up.

Thanks!
RW
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,307
you pull the elbows off the manifolds and you inspect.

rust streaks are signs the gasket is failing/failed

if the risers and manifolds are used in salt and older than 5 years, inspect

if they are older than 10 years, replace

during inspection:

if the lands for the gasket are thinner than about 5mm (3/16"), replace

if the mating surfaces dont clean up with a few passes of a large bastard file or a belt sander, replace

if the passages are rusted shut, replace
 

Lou C

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Nov 10, 2002
Messages
11,802
NOTE:
drain raw water out before breaking loose elbow (riser) so that water does not spill over into the center gas passage.
do as Scott above suggested. If the sealing surfaces are getting eroded/thin then its time to replace, also they could be very close to rust through in some places that you can't see. Get some longer than standard bolts (compare to your new bolts that will come with the new exhaust) cut the heads off and then cut a slot in the end. This will allow you to thread the head less bolts in (2 are all you need) to keep the exhaust manifold gasket lined up while sliding on the heavy exhaust manifold. You could do the same with the bolts that hold the elbows to the manifolds, just get 2 longer bolts same threads this way you keep the gasket and holes aligned....
 

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RussWalters

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Jun 25, 2018
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Thank you both, great tips. Is there anything other than the Risers/Manifolds that I should be looking at to see if water got into the engine and potentially causing issues?
 

Lou C

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Well when you look into the center exhaust gas passage if there is evidence of rust in the center, then it could have gotten into the cyls. When you remove the manifolds, look in the exhaust ports in the manifolds and cyl heads, for rust. You should just see black carbon there. When you install your new ones you have a choice, you can use aftermarket manifolds/elbows (but good ones like Barr Marine) and use their gaskets, or use the OE VP ones
 

RussWalters

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Jun 25, 2018
Messages
34
Well when you look into the center exhaust gas passage if there is evidence of rust in the center, then it could have gotten into the cyls. When you remove the manifolds, look in the exhaust ports in the manifolds and cyl heads, for rust.

Ok, that makes a lot of sense and was just what I was looking for.

One more follow up, The large hose that connects to the water pump is getting REALLY hot, like only able to keep hand on this hose for a couple of seconds hot. Any other issue I should be looking at here, or Risers/Manifolds a good place to start?
 

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Lou C

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Normal for the big hose from the thermo housing to the water pump to get too hot to hold. As soon as the t stat opens it let’s hot water exit the block that’s what you are feeling; it will be about 150-160* F.
 
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