correct riser gasket? Restrictor or Full flow? 76 351w

[FstaRockr Burns]

Hi all - SO i pulled my risers and manifolds and found if I blocked the manifold water pipes and filled the jackets the water stayed put. When I tested the risers, about half way they started filling the large main exhaust chamber - i thought oh no, im done for - but it appears the risers are supposed to send water down the exhaust ports according to this old boffin -

http://www.yachtsurvey.com/exhaust_risers.htm

"All marine inboard engines have exhaust risers. The exhaust riser has two functions: (1) to keep water from backing up into the engine through the exhaust piping and, (2) it serves as the device that introduces cooling water into the exhaust exit piping system.


So assuming my bits are actually ok and working as should (hardly any corrosion on the outside and inside is still solid metal) - what is the correct riser gasket to use? Mine had a small hole on both risers - is thi

 

[Bt Doctur]

it serves as the device that introduces cooling water into the exhaust exit piping system.
AFTER it exits the elbow ,not before. Water inside the riser is a sign its leaking or a gasket has failed.

 

[Bt Doctur]

http://www.michel-christen.com/ExhaustElbows.pdf

 

[kghost]

Hi all - SO i pulled my risers and manifolds and found if I blocked the manifold water pipes and filled the jackets the water stayed put. When I tested the risers, about half way they started filling the large main exhaust chamber - i thought oh no, im done for - but it appears the risers are supposed to send water down the exhaust ports according to this old boffin -

http://www.yachtsurvey.com/exhaust_risers.htm

"All marine inboard engines have exhaust risers. The exhaust riser has two functions: (1) to keep water from backing up into the engine through the exhaust piping and, (2) it serves as the device that introduces cooling water into the exhaust exit piping system.


So assuming my bits are actually ok and working as should (hardly any corrosion on the outside and inside is still solid metal) - what is the correct riser gasket to use? Mine had a small hole on both risers - is thi

You can use this web site as a parts source.

Better sometimes than asking any of us............


http://www.marineengine.com/parts/m...4/exhaust-manifold-and-exhaust-elbow-assembly

 

[kghost]

Another pic for reference

 

[RicardoMarine]

................................

Hi all - SO i pulled my risers and manifolds and found if I blocked the manifold water pipes and filled the jackets the water stayed put.
Assuming that you have an "open" system (i.e., raw water cooled engine), if your manifolds look like what Jack posted an image of, you will have 2 ports per manifold.
One is a coolant supply, and the other is a coolant return. (coolant being raw water)

When I tested the risers,
Again, if your system is like what Jack posted an image of, your system does not have "risers" (spacers)!
Your system has manifolds and elbows only.

about half way they started filling the large main exhaust chamber - i thought oh no, im done for - but it appears the risers are supposed to send water down the exhaust ports according to this old boffin -
Yes, within the elbow is the "mixing" chamber where the "spent" seawater (aka coolant) enters the exhaust flow.
Since the manifolds have the two coolant ports (supply/return), and since the elbows are also ported, the seawater transfer ports (the ports between manifold and elbow) must be blocked off.


So assuming my bits are actually ok and working as should (hardly any corrosion on the outside and inside is still solid metal) - what is the correct elbow gasket to use? Mine had a small hole on both elbows -
The gasket/plate primarily blocks transfer port flow. The small hole is a weep hole to allow the elbow to drain.

 

[FstaRockr Burns]

ok well thanks for excellent info guys - kghost gr8 diagrams there.

So i think all might be ok - i noticed the elbows only started entering the exhaust chamber when they were about half full (upside down) indicating that the water enters at some point, like it has a catchment chamber or something.

The gaskets were in great shape, no leaks or rusting - there was zero rust around them or any sign of leaking.

I will pump out the oil, re-assemble and run till its moderately warm and check oil..

Another possible culprit might be the intake gasket - which I might replace as a precaution.



*** So if i had assembled everything and blocked off the incoming water hoses to risers and from back of motor - the water would still have exited thru the risers with a pressure test? So im supposed to block off the exhaust manifolds with risers removed?



​Sorry for the repetitive dumb questions!

 

[FstaRockr Burns]

it serves as the device that introduces cooling water into the exhaust exit piping system.
AFTER it exits the elbow ,not before. Water inside the riser is a sign its leaking or a gasket has failed.

Thanks - but if i may add:

[FONT=&quot]At the aft end of the riser, water from the water-jacket combines with and cools the hot gasses before continuing out the exhaust overboard discharge.

So at some point water DOES exit the riser. in my case I noticed water only filled the jackets half way (upside down / plugged and removed from engine).

A BIG note - while the motor was running, nothing heated up.. the risers would stay warm on both sides.. I meticulously monitored the temps during the first few runs.

Also the boat stood for a while and theres a chance some rain water entered thru carb by accident.

Ill try run her with some clean used oil.. it only takes about 5 mins for water to show up..[/FONT]

 

[FstaRockr Burns]

Oh BTW - I see the weep hole allows the water thru, great to understand how these things work!

 

[FstaRockr Burns]

Another pic for reference

Tx, do you possibly have a higher res pic?

 

[RicardoMarine]

FYI.... what you all calling a "riser" is an "Elbow"!
Your system (if like what Jack's image shows) does not use Risers/Spacers!

 

[FstaRockr Burns]

FYI.... what you all calling a "riser" is an "Elbow"!
Your system (if like what Jack's image shows) does not use Risers/Spacers!

Ah sorry - my bad, elbows then.. new to marine engines

 

[FstaRockr Burns]

FYI.... what you all calling a "riser" is an "Elbow"!
Your system (if like what Jack's image shows) does not use Risers/Spacers!

On closer inspections, I DO user risers, so you have either misunderstood me or have the wrong terminology yourself. The manifold bolts to the riser which in turn meets the elbow that joins to y pipe.

The manifold and riser are what you check leaks for - the elbow is simply just an elbow / bend.

 

[FstaRockr Burns]

So what is he doing this for?

http://forums.iboats.com/forum/engi...nifolds-risers-and-elbows-as-a-unit-for-leaks

 

[kghost]

AGAIN

NOPE.

Apples and oranges................

Yours = Ford and old style
That picture = New style and Chevy

Why is he doing this, to pressure check it. If you had this set up that is what you would be doing.......

Water flows up from the bottom of the manifold (see fitting) and out the elbow. Some also have a fitting in the elbow for all the time cold water to the exhaust but the thermostat housing is different based on design.

 

[kghost]

Here is a flow diagram with that style manifold and elbow. This one has the second hose going to the elbow for full time cold water to the exhaust

Notice the gasket between elbow and manifold has the holes to allow water to flow thru. Yours uses block off plate sandwiched between the gaskets I think with a tiny hole to allow steam to escape.

 

[FstaRockr Burns]

AGAIN

NOPE.

Apples and oranges................

Yours = Ford and old style
That picture = New style and Chevy

Why is he doing this, to pressure check it. If you had this set up that is what you would be doing.......

Water flows up from the bottom of the manifold (see fitting) and out the elbow. Some also have a fitting in the elbow for all the time cold water to the exhaust but the thermostat housing is different based on design.

Ok thanks - sorry! So to confirm, its totally correct when I:


* Turn riser upside down / level
* Block the water hose connections with corks
* Pour water into water jackets

Inside / exhaust area stays dry until half way, then the water "overflows" into the main area?

Bear in mind - the risers do not overheat, plugs are all same color, no weeping on gaskets, no rust inside exhaust chambers anywhere indicating water flowing backwards -

Apparently a dry powder color everywhere inside exhaust area indicates risers arent leaking..?

 

[bondo]

Apparently a dry powder color everywhere inside exhaust area indicates risers arent leaking..?

That's correct,...

Have ya pressure tested the motor's Block,..??

 

[FstaRockr Burns]

That's correct,...

Have ya pressure tested the motor's Block,..??

Nope not yet - got a kit yesterday for radiators, its a rental so cant really b changing stuff around, but will see what I can do today with some spare bits lying around..

Will buy a pressurize hand pump soon I can make work on anything..

Im suspecting possibly water entered thru carb maybe, OR intake is leaking.. a cracked block would allow water into the comb chamber = plug would show it?

 

[RicardoMarine]

1.... On closer inspections, I DO user risers, so you have either misunderstood me or have the wrong terminology yourself. The manifold bolts to the riser which in turn meets the elbow that joins to y pipe.

2... The manifold and riser are what you check leaks for -

3... the elbow is simply just an elbow / bend.

1..... See post #5 again. Are we not talking about the "log style" manifolds and rear elbows as Jack shows us?

If so equipped, Risers/Spacers would install between the manifold and the elbow! Sometimes they are used to elevate the elbow….... Sometimes they are used for an additional coolant port!
Nonetheless, if you have a component like this, it would indeed be a riser/spacer.


2.... Yes

3.... All marine exhaust elbows incorporate interior porting for the "spent" seawater. This becomes the path to the mixing chamber where the seawater enters the exhaust flow.
Elbows are more difficult to pressure test.



.

 

[Bt Doctur]

Have no clue as to what is being tested in that pic but any air introduced into the bottom of the manifold will leak out the exaust ports.
Did you open the link in post 3?

 

[FstaRockr Burns]

Have no clue as to what is being tested in that pic but any air introduced into the bottom of the manifold will leak out the exaust ports.
Did you open the link in post 3?

yes had a look, i just wasnt exactly sure what to test.. either way, drained old oil and threw in about a gallon of diesel and crank her over a bunch o ftimes with plugs out - im busy pulling half the stuff off the motor for a paint and inspection - will do intake 2moro as a precaution as they also tend to leak and at this point i have almost everything off except heads - replacing all the gaskets, at least it will give me peace of mind that ive looked thru everything.

Ill prob end up ordering a pressure pump so i can block off water pipes and pressurize the block and see -

 

[bondo]

Ayuh,... Once ya pull the intake off, ya can't pressure test the block,.....

So do that 1st,....