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exhaust manifold and risers

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Old 01-12-2018, 04:35 PM
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Default exhaust manifold and risers

Sorry if this has been asked before. When removing the exhaust manifold and risers on Horizon 8.1S on SeaRay 380 SunDancer, I am aware that the raw water valve need to be closed. I also read that the exhaust hose after the riser needs to to be blocked/plugged and tied up above water line to prevent flooding the bilge and sinking the boat. Makes sense to me. I can certainly figure out how to tie up the hose above water line but what would any of you recommend as a way to plug or block that larger size hose when pulling off the riser?


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Old 01-13-2018, 06:20 AM
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It sounds like you're changing the manifolds with the boat in the water, right? If so then your concern is water that can flood into the boat from the Y pipe. This is hard to give you advice on because it depends on how high up the static water line is in the Y pipe when the boat is in the water. It is possible to fab up a cover for the Y pipe opening from flexible rubber and one of the hose clamps used to hold the rubber exhaust hoses to the Y pipe. However keep in mind that this is risky, most people would pull the boat out to do exhaust risers and manifolds. Post up a pic of your exhaust set up....
What you have to think of, is what happens if, you get stuck in the middle of this job with a bolt that won't come out and then whatever you fabbed up to keep water out fails and water starts flooding in? Your bilge pumps will only keep up for so long!

In this pic you can see the upper end of the Y pipe behind the exhaust manifold, on this boat the static water line puts the water level in the pipe pretty close to the top.

Keep in mind in order to install the riser you may have to remove that rubber hose on top of the Y pipe.
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Last edited by LouC; 01-13-2018 at 06:34 AM.
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Old 01-13-2018, 08:39 AM
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Thanks Lou. I will check when I am back down at the boat. Boat in Hilton Head I am back in NJ as of last night. I believe in this boat the critical stuff is above the water line.
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Old 01-28-2018, 05:28 AM
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Yes, no need to worry about water coming aboard. I changed my manifolds and risers in my Catalina, like your boat everything is way above the waterline to have any water coming in.
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Old 01-28-2018, 06:14 AM
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If that engine is a full fresh water cooled engine, why are you replacing the manifolds?
If that engine is a 1/2 fresh water cooled engine....never mind
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Old 01-28-2018, 06:16 AM
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Old 01-28-2018, 02:36 PM
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Thanks to all of you who replied. It was a fresh water boat first owner. No more. And it is a raw water manifold with coolant in block. I pulled the manifolds out last week in the water. Yes the y pipe is above sea level and the raw water through hull is closed. Boat still floating. :-)
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Old 02-01-2018, 07:29 AM
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Glad it worked out. Now just put yourself on a 5-7 year replacement schedule.
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