Mannies & Risers, reuse or replace

[AKJohne]

1997 5.7 LX, San Juan HE, closed cooling,
This motor was originally in a Alumaweld, now in a Glasply. 200 hours freshwater, 140 hours in saltwater. After several years of work we finally launched this spring. I had removed the riser/elbows, cleaned and installed with new gaskets. We had to routinely add coolant over the course of the year. Season is now over, I pressurized the HE and it lost a few PSI and spotted the floor (exhaust) with coolant overnight. Cracked the drains on the elbows and sure enough.... coolant. Now that I know I will check that much sooner. No coolant in the engine.

Today I pulled the risers and the mannies and sure enough the gasket had failed, surface not as flat on the mannie as it could/should be. When I removed the riser some coolant went in the exhaust manifold, fortunately it was only one cylinder and that valve was closed (can this be avoided?). I was thinking I would need new risers and was considering converting to a dry joint as things were looking kinda ugly. Once I cleaned everything up I am now thinking I can reuse everything once I have the mating surfaces reground.

 

[AKJohne]

See if this works

 

[AKJohne]

A few more,

 

[AKJohne]

This is the view in the exhaust ports, I did some coolant in the valve pocket, once I removed the mannie I daubed up the coolant. The cylinders were dry, luckily those valves were closed. Once I had it dry I put some oil in each port, turned the motor over and squirted some more oil past the valve to the top edge of the piston. And finally rotated the motor over several times..... suspect it may smoke a wee bit when I fore it up... Question is..... how to prevent this in the future when pulling a manifold...?

 

[AKJohne]

Then I plugged the fitting and poured in some muriatic acid and let it soak for a while, flushed with hot water and then wire brushed the passages as best as possible. If I have the surfaces reground can these be used? Or is there any reason not to?

 

[AKJohne]

I know, lots of pics....maybe too many... In case other than the "can I use these" question, I have a few more.
Best gasket and sealant type?

I am thinking I may need a taller riser, new exhaust flaps however the top of the riser is above 11-13" above the water line, I have ~ 3'' of room to the inside of the cover. Can I use a extension? Will I need new rubber exhaust connector at the exhaust horn?

Any Advice will be appreciated, thanks

 

[achris]

Ok, those elbows and manifolds look ok. Quite reusable. However, your waterline to top of elbow height is under spec. The spec is a minimum of 13" (as per the drawing below). You should add a 3" kit. A kit consists of two 3" risers, the required gaskets and fixing hardware. As you have a closed cooling HE, you'll need to put a block-off gasket between the manifold and riser on each side (part# 27-41811, and for those, I only use Merc). You will also need two new exhaust tubes (the ones between the end of the elbow and the top of the 'bull-horn' collector.

Risers for a 'wet-joint' V8 system is -93320A13 (1 required, 2 in the 'kit')
for the longer tubes, -14801A1 (1 required, 2 in the 'kit') They come as 6". To use with 3" risers, you remove the lower 3".

Chris...........

 

[AKJohne]

Thanks Chris, any sealant used on the block off gasket? Full flow gasket at extension and elbow?

 

[tpenfield]

FWIW - You should drain down the coolant from the manifolds before you open up the joint. I assume that you've had to add coolant along the way?

 

[achris]

Thanks Chris, any sealant used on the block off gasket? Full flow gasket at extension and elbow?

No sealer on the gaskets. The Merc gaskets are graphite impregnated, so they seal very nicely.

Yes, full flow between riser and elbow. Also, the water exiting the HE that now goes into the elbow, needs to go into the riser. So remove the nipple from the elbow, put a plug in that hole and put the nipple into the riser....

Chris.....

 

[scoflaw]

If that was my rig, I would make the riser part of the AF side. Plug the AF exit on the manifold and put the return nipple in the riser. Leave the elbow as is. Open gasket between manifold and riser, closed gasket between riser and elbow

 

[AKJohne]

FWIW - You should drain down the coolant from the manifolds before you open up the joint. I assume that you've had to add coolant along the way?

Thanks, I guess thats what the blue drain plugs are for... duh... I did have to add coolant every time we went out, it was a concern.

 

[AKJohne]

If that was my rig, I would make the riser part of the AF side. Plug the AF exit on the manifold and put the return nipple in the riser. Leave the elbow as is. Open gasket between manifold and riser, closed gasket between riser and elbow

Thats a interesting thought as it would theoretically increase the life of the riser to the same as the manifold, any potential downside to this arrangement?

 

[scoflaw]

That's how my 0w345831 was set up from Merc.

 

[AKJohne]

I mocked up a 3" riser and put the cover back on and using a 2 X 4 it looks like I will have about 3/4" clearance between the top of the riser and the fiberglass cover. Is the overall consensus to cool the riser from the AF side?

Thinking I will R&R the valve cover gaskets, is OEM the way to go for this? Anything else I should be thinking about?

THANKS....

 

[AKJohne]

Finally back on this, winters are long in AK, The elbow kit 14801A 1 showed up today, however the bend is different than the old one. Did I get the correct part? Was the old one wrong? ​​​​​​​

 

[achris]

A quick search suggests the old pipe was for a 14 degree elbow. 14 degree elbows were never available as wet-joint elbows, only dry-joint. As you have wet-joint manifolds and elbows, that would suggest the old part was the wrong one... Can you post a photo of the exhaust elbow side on?

Chris........

 

[AKJohne]

As always, thanks Chris for your reply and help...
See attached pic/s, that would explain why the elbow/rubber/elbow connection never looked quite right, however I think it was ok in terms of water flow at the top of the cast elbow. Curiously I am the third owner of this 1997 motor and am reasonably sure these were all original components as the motor failed with in a few hundred hours and was removed from boat and placed on a pallet for years.

I had the cast elbow mating surface redone, around here they use a large belt sander, I am not stoked about the finish although I believe it to be flat, what say you guys?

 

[Lou C]

I'd say they need to go over that again with finer paper. When I installed the new exhaust on my engine back in '17 the sealing surfaces were a lot smoother looking, very light machining marks and flat to less than .001"

 

[AKJohne]

​​​​​​​I spent some time tuning up the mating surfaces on a piece of quartz with some lapping compound, pretty happy with the results. I did notice what appears to be tiny cracks in one of the risers I bought (used). It seems pretty minor, however if it is a crack it will only get worse. What do you guys think...? Something to be concerned with?