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Bad Riser?

Old 09-02-2020, 12:16 PM
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Hello All

Just wanted to start by saying that this forum is amazing and I love reading through all the builds from people who have WAYYYY more experience and know how than myself.

I've just finished building my engine for my 97 advantage citation. It started life as a 500HP blue motor that was putting water in the oil. I diagnosed leaking mercury manifolds and replaced them with a set of Hardin Marine cyclone headers and kept the risers that I was using before. they look like they are cut down GIL big guns and the boat has a under platform exhaust exit. It now has a full eagle rotating assembly with a comp 295-011008 cam. the block and heads were cleaned and magnafluxed. The Heads also had .004 thousandths taken off at the machine shop.

Upon assembly completion i pressure tested the long block, the headers, and the oil coolers. All of which held pressure. I am still having the issue of water mixing with oil. The dipstick is showing clean oil but under the valve covers show a different story. I have about 45 minutes or so of run time on this engine and would like to solve the problem ASAP. The only issue that i saw on my maiden voyage was water seeping between the riser/header gaskets. Since this is a dry joint, I was a little surprised that water would be getting to that area and I suspect that this is how water is entering my engine.

My question is, has anyone seen a failed riser? it is hard to pressure test them but I am at a loss on what else it could be.

Thank you for the input.
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Old 09-02-2020, 02:17 PM
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Just a thought but under platform exhaust are notorious for swamping engines on certain ramps. Not sure if it is backing in too fast or what. Also External and Internal flappers are a must on those type of applications.

Chris
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Old 09-02-2020, 10:17 PM
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Originally Posted by Blueabyss View Post
Just a thought but under platform exhaust are notorious for swamping engines on certain ramps. Not sure if it is backing in too fast or what. Also External and Internal flappers are a must on those type of applications.

Chris
I thought of that too. The boat does have flappers on it that seem to be in good shape but I'm not ruling that out. I pulled the risers off this evening and both headers had moisture in them but the Starboard side had much more water in it (puddles at the top near the riser flange). I'm going to re-pressure check the manifolds tomorrow but its not looking good for them.
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Old 09-03-2020, 10:13 AM
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Originally Posted by Blueabyss View Post
Just a thought but under platform exhaust are notorious for swamping engines on certain ramps. Not sure if it is backing in too fast or what. Also External and Internal flappers are a must on those type of applications.

Chris
Exactly what happened to me. Flooded both rear engines. Unfortunately, I didn't catch it until one quit. Engines are out & being rebuilt now. I made a setup with rubber balls with rope attached to block the below platform exhausts when ramping in & out. Hope to try it soon. Hope this helps.
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Old 09-03-2020, 10:34 AM
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Just under the valve cover may be condensation, if you are just going for shorts runs and not getting up to temp long enough to evaporate the condensation from the previous run it can build up.
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Old 09-14-2020, 12:37 PM
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Just an update, I did a pressure test on both headers last night with water in the exhaust side and air pressure in the water side. I pressurized the system to 15 psi and saw no bubbling or air leaking through to the exhaust side. Not sure where the water would be coming from unless the risers do in fact have a hole in them somewhere. When i removed them, I saw no evidence of a leak around the welds.
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Old 09-14-2020, 01:05 PM
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What are your cam specs??? It could be reversion due to cam overlap. Stock HP500 cams were known to cause water reversion at idle
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Old 09-14-2020, 09:28 PM
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If the oil in the dipstick is clean then I agree with resurrected...... its just condensation. If there was water getting into the oil it would really be whipped up to a froth and showing on the dipstick.

What oil are you running ? Oil temp ?
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Old 09-14-2020, 09:49 PM
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A leak at the riser/manifold gasket will cause reversion. First thing you need to repair is that leak.
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Old 09-15-2020, 09:55 AM
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Originally Posted by Unlimited jd View Post
A leak at the riser/manifold gasket will cause reversion. First thing you need to repair is that leak.
I'm ordering new gaskets today so hopefully that fixes the issue.
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