Exhaust riser leaking. 2010 6.0L

Hey everyone, first post here and I am hoping you can help me out with a problem I am having.

I have a 2011 Nautique ski boat which has the 2010 Crusader 6.0L motor. Towards the end of last year I had an overheat and one of the exhaust risers cracked through inside causing the coolant to just run right through out of the exhaust even with the motor off. We replaced both the exhaust risers using the gaskets sent by Nautique. The mechanic doing the work had a hard time getting the risers to seal properly onto the exhaust manifolds and ended up using some gasket seal on the one side. Eventually they appeared to seal and we tested the boat and it ran just fine. I have been using the boat since and it has been running as before. The coolant level has not changed noticeably and I have done about 60 hours on the motor.

During the 60 hours performance has been normal but I noticed that on starting the boat first thing in the morning it would stutter occasionally and almost stumble to life. I feared that there was a small leak somewhere but the mechanic reassured me that if the boat was running smoothly it was ok. I winterised the boat and recently got it back out the garage for the summer here (South Africa). Before I ran it I pulled all the plugs and everything seemed normal. I also changed the FCC fuel filter and the in-line filter as I thought water in the fuel may be causing the bad starts. Today I took the boat out and inspected around that gasket very closely and saw a tiny leak on the outside. The boat was running fine and the leak appeared to be very slow. I remain concerned though...

- Is there likely to be a leak causing the bad starts on the inside?
- Have I caused damage to the engine by running it with this leak for 60 hours?
- What are the correct gaskets for this engine and what is the recommended way of getting them to seal properly.

I really appreciate any help with this one and I apologise for my somewhat limited mechanical knowledge. Let me know if you need any further details.

A minor water leak into the motor via the exhaust system will not hurt the motor when it's running. When starting, however, with a slug of water in the cylinder, this can destroy a piston and bend a rod!

Having had this problem for years, I'v gotten into the habit of carefully spinning the motors over after they've sat for a few days--it takes that long for the water to drip into where it should not be. Many times I've put to pull the plugs out and blow the water out. Nasty!

That joint should NOT leak--period. Millions of them don't, so why is yours (and mine)? Time to do a bit more silicone sealing, despite what the manifold/ riser instructions say; they don't want EXCESSIVE silicone plugging the water exit holes.

Here's what's happening: Heat cycles and time have warped the gasket mounting surfaces so that they don't seal properly, and even with a nice, thick gasket. If you can't get the surfaces remachined flat, then a god silicone job is the answer. And be sure to let the goop cure overnight before firing her up.

Jeff

The gasket should either come with a blockoff plate or have one incorporated (a stand alone sandwich)...this keeps the coolant in the maifold and the raw water in the elbow...Like Jeff suggests, the mounting surface of the manifold could have warped during/after the overheat event....

I'd suggest removing the elbows and inspecting their mounting surface on the manifold with a straight edge...if it isn't too bad, you can draw file it flat...if its really bad, a machinist should be able to flatten it out...I'd use something like perfect seal (permatex #3) on the gasket (unsure what is readily available over there)...

Thanks for the quick response guys. I am going to get them off as soon as possible and clean them up nicely, see whats going on. Will post an update when I get to it.

Good condition manifolds, spacers/risers and elbows should NOT require any gasket sealant.
In fact..... many of today's gaskets instruct that we DO NOT use sealant.
If they do, you likely have un-flat mating surfaces that need attention.
You may want to question your mechanic's credentials!


An E/G (ethylene glycol) leak is certainly better than if seawater was leaking into a cylinder.... but nonetheless, neither is a good sign.


Until you resolve this, you have several options:

• Once cooled down, release the H/E coolant pressure.
• If your seawater pump impeller is easily accessible, remove it and do a 8 to 10 second dry start when putting the boat away for lay up.

With the impeller removed, a quick 8 to 10 second dry start will not harm anything, and it will ensure that no resilient water has remained near an open exhaust valve. (I've been doing this for as long as I can remember)


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