Manifolds and Risers

[lifespan]

Thanks again Mike. Just realized all my misspelled words in post. It was late. I understand. Sad part is, I don't have a history on boat before last owner. Even then, I don't have much from him. My assumption is that he never replaced manifolds or risers. The boat was owned by someone in Huntington Beach California, so assuming salt water use. Need to move ahead and replace all. Out of curiosity, when riser is running hot, any way of knowing if failure is riser or manifold? Also, assuming nothing has ever been changed and both running lower than 150, is that a reliable indicator of proper function? And can you measure temps out of water running engine with water muffs? I assume that you would have to run at full throttle?

[lifespan]

Just in process of pulling the riser. Mine have the cast spacer. Trying to lift riser of above bolts but, can't manipulate over bolts while riser attached/connected to rubber sleeve. What's the best way to get that sleeve slid back so that I can get riser above top of bolts and remove? Can't pull riser out toward me because of bolts. Make sense?

[mmwjr]

Ok for correctness a lot of folks call the elbow a riser but the riser is really that spacer you mentioned.

Elbow typically fails before the manifold, cracks form where the raw water is injected into the exhaust stream.

Never run the engine much above idle on muffs, may not be enough water flow to cool. Also the water hose may collapse from the pumps suction if a cheap hose.

To remove your set up loosen the other end of the rubber hose where it connects to the Y-pipe, this will also allow you to inspect the flappers which probably need to be replaced.

What engine and drive do you have?

[lifespan]

5.0 alpha gen 2

[lifespan]

And after loosening clamp on hose connecting to y pipe, I would just pull that whole pipe out along with the elbow, leaving it all connected?

[mmwjr]

Originally Posted by lifespan

And after loosening clamp on hose connecting to y pipe, I would just pull that whole pipe out along with the elbow, leaving it all connected?

You want to remove item 1 - 3 with the elbow

Loosen the lower clamps then use a flat blade screw driver to break the seal between the hose and y-pipe

[lifespan]

Pulled the elbows today and wow! Completely closed off with rust, flaking everywhere. Jacket was really bad. The one that was running hotter was worst. The other, although seemingly running normal temp, was really bad as well. Not sure how to post pictures here, but would love to do that if someone knows how.

In the market now for the entire kit. Any best resources, with best prices for manifolds, elbows, risers and all gaskets?

[Kevlar7r]

I haven't ordered mine yet, but while looking around, go2marine.com seems to have good prices. I am going to go with aftermarket ones.

[lifespan]

Thank you. I did see them. I would imagine that providing them the engine serial number would make sure I get order exactly right?

[Kevlar7r]

The 5.0l and the 5.7l take the same headers/risers/elbows throughout their history (with a few minor exceptions). I haven't seen one whole kit that has everything, so you'll have to order the manifolds, spacers, risers separately. Just as long as they all say for small block Chevy or 5.0l or 5.7l.

[mmwjr]

There are kits but they are manifolds and elbows only.

I would also replace the flappers while you have it apart.

[lifespan]

That's the kit I was referring to. So, as I attack this, I was just reading a warning when removing the manifolds. It indicated that many people, including mechanics, leave exhaust ports unplugged when removing he manifolds, leading to the sinking of the boat. First off, what are the exhaust ports? And how are they unplugged during the removal?

[mmwjr]

First this only would apply if the boat is in the water while performing this task.

They are referring to the y-pipe passages being left open, if the top of the pipe is below the water line water will flood the boat.

[lifespan]

I mentioned pulling the elbows and finding significant rusting and obstruction. Will also be replacing manifolds, basically entire exhaust components. My question is, will mostly a very inquisitive wife, is there any engine damage or corrosion issues given the state of the elbows and assuming the manifolds?

Engine starts and runs smoothly, especially with rebuilt carburetor, good compression, I am assuming. Never a hydrolock that I understand means water in cylinders. Good oil pressure and temperature. It's there anything that I would notice symptomatically or objectively to rule engine damage?

[mmwjr]

Water in the oil or a tuliped exhaust valve (melted seat) are the common signs of water ingestion from leaky exhaust.

Sounds like you caught it in time.

[lifespan]

Didn't see any water in oil. What would signs be will tuliped valve failure?

[mmwjr]

Originally Posted by lifespan

Didn't see any water in oil. What would signs be will tuliped valve failure?

Bad compression. On a boat I boat it was zero psi as the valve did not seal at all.

Burning water raises exhaust temps so the exhaust valve or seat fails.

[Kevlar7r]

Here are the manifolds I just ordered from go2marine.com. Thought this might help you.



As far as plugging the exhaust ports. Once I removed the riser from the rubber tube, I plugged the rubber tube with these test plugs from home depot. See pics.

[lifespan]

Ordered new manifolds, risers and elbows. When reinstalling manifolds, what is the best way to make sure that manifold gasket remains positioned correctly as I connect manifold? Should I use a spray adhesive to secure? If so, what can be used? The same question for the gaskets between riser and manifolds and elbows and risers.

Lastly, best way to clean gasket surface between engine and manifold?

[mmwjr]

For removing the old gasket use a gasket scraper that you can get from an auto store. I then clean it up with fine sandpaper. Stick a shop towel in the exhaust ports to keep debrie out.

You can get gasket adhesive to attach the gaskets to the manifolds or use a piece of all-thread in the end holes to get started, then install the center bolts. Now remove all-thread and install bolts.

Riser and elbow gaskets should just drop in place.