Intake/Exhaust manifolds .....Risers......

[petes penn]

Ok so GM 350.......How does one know when their exhaust manifolds and risers are bad? Tell Tale signs? Mine look ok but I am not entirely sure what to look for.


Also, Intake Manifolds. Marine manifolds I am told are lined with brass or bronze whereas auto/truck are not. I understand this is for corrosion resistance, however is there a need for this if you ffresh water flush your boat after taking out of the water? I live on the east coast and my boating will conist of primarily saltwater......river and ocean. If I flush everytime I remove the boat......no mooring or dock space........wil this be sufficient or should I spend $400+ on a new intake manifold?

I can provide photos if needed......

 

[littlebookworm]

Re: Intake/Exhaust manifolds .....Risers......

How old is the engine? How many hours of use has it had? My understanding is that, in salt water use, exhaust manifolds and risers will last about five seasons. You really can't tell from looking at the outside, you have to take a look at the inside; and even then it's a bit of a guessing game. Since a failed manifold or riser can kill your engine, a good rule of thumb, to me, is: "If in doubt, throw it out." As to the intake manifold, I've never heard of one being lined with anything. Look at the water jacket, where the thermostat housing goes, to see if there is much corrosion, If so, it needs to be replaced. The same goes for any area around water flow openings. If everything looks OK and there are no pieces rusted off, then you should be OK. Good luck and safe boating. Hy

 

[leoo24]

Re: Intake/Exhaust manifolds .....Risers......

Having just bought a boat and gone through the same process with my risers and manifolds i'm still fresh on what i've learnt...

rust on the outside of the gasket shows water is leaking out, which means it is more than likely leaking into the gas only chamber also. As littlebookworm says, take the risers off and inspect for signs of rust inside the gas only chamber (the center chamber), also look at the gasket surfaces, any pitting from rust there will prevent a proper seal and allow water into the gas only chamber.

I could have milled my gasket surfaces but decided to play safe and order new ones

good luck

 

[JustJason]

Re: Intake/Exhaust manifolds .....Risers......

is there a need for this if you ffresh water flush your boat after taking out of the water?

That's a nice thought.... but you won't. Not after you get home at 10pm and park the boat in your yard. You may the first couple times, but not in the long run.

They make marine specific for a reason. I guess it's up to you wether you really "need" it or not. Just don't be upset if you have a rotted manifold and a crankcase full of water and spun lower bearings after 2 seasons.

 

[petes penn]

Re: Intake/Exhaust manifolds .....Risers......

That's a nice thought.... but you won't. Not after you get home at 10pm and park the boat in your yard. You may the first couple times, but not in the long run.

Good point......marine it is, after all the damage is being done out on the water.

Some pictures on the exhaust manifolds and risers.....

http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1973.jpg
http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1974.jpg
http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1975.jpg
http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1976.jpg
http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1977.jpg
http://i31.photobucket.com/albums/c383/picasso928/Boat/DSCF1978.jpg

Thanks again.......

 

[Bondo]

Re: Intake/Exhaust manifolds .....Risers......

Ayuh,...

Those manifolds look like they've been Leaking,... For Awhile.....

As for the Intake Manifold,.....
Cast Iron I believe it the Prefered saltwater Marine manifold....

You'll only see the bronze lining in the water passages of Very Hi-end Aluminum intake manifolds....

 

[petes penn]

Re: Intake/Exhaust manifolds .....Risers......

Alright......so do you think new gaskets will solve the leaking issue? the bolts on the risers look like they are hurting.....probably will break if I try to remove them. My guess is that new/remanned is the approach?

Picture #2 and #5 .........should that rust bonding both surfaces be there? I thought it was supposed to be obstruction free? My thought is that if that is there, the water flow will be inhibited........but I am new to this so what do I know anyway.......

 

[Maclin]

Re: Intake/Exhaust manifolds .....Risers......

The part you need to look at is on the inside anway, so "break a leg" .....or a bolt or 2....

 

[JustJason]

Re: Intake/Exhaust manifolds .....Risers......

Don't even bother seperating the risers....
The outlets on the risers look awefully clogged, i would bet the insides not any better.
Besides, when manifolds go bad, if not caught they take the engine with it.
Do you really want to trust your new motor and all your work to the integrity of those old manifolds?

 

[bolo78910]

Re: Intake/Exhaust manifolds .....Risers......

best to chang both, if you dont hav the loot at least change those risers, they look aful closed