Manifold/ Riser Question 8.1 Horizons

Misterhelms

Active Member
Jul 5, 2020
104
Monmouth Beach, NJ
Boat Info
2004 Sea Ray 340 DA
Engines
8.1s Mercruiser
Currently on a sea trial on a 2007 340 and 3 of the 4 risers are running hot around 195 degrees at cruising speed. The 4th riser on the far port side is showing 120 degrees. Any idea why 3 of the 4 risers would be running hot?
 
This is a can of worms. Could be so many things. Insufficient water flow caused by ..laundry list of things. My guess is there may be clogs limiting water likely caused by excessive rust inside the manifolds. Either way it’s a problem. Is the boat in salt? Manifolds need to be changed every 5 years. Find out when they last did them.
 
Yup those are way way overdue. It’s going to be a $5k job minimum. Parts alone will be in the $3k range. Also make sure you check the oil assuming he’s hasn’t changed it recently. Check for water in oil etc. Its not typical for these dry joint manifolds to leak into the engines, but it will happen eventually. Then you’ve got a whole bunch more problems.
 
Yup those are way way overdue. It’s going to be a $5k job minimum. Parts alone will be in the $3k range. Also make sure you check the oil assuming he’s hasn’t changed it recently. Check for water in oil etc. Its not typical for these dry joint manifolds to leak into the engines, but it will happen eventually. Then you’ve got a whole bunch more problems.


For the OP, if you buy the boat and have this done post the pictures of the risers here.
 
For the OP, if you buy the boat and have this done post the pictures of the risers here.
Looks like the owner is going to get them replaced which is great. That was one of my main concerns about buying a boat. I took the below pictures today on the sea trial
 

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Yup those are way way overdue. It’s going to be a $5k job minimum. Parts alone will be in the $3k range. Also make sure you check the oil assuming he’s hasn’t changed it recently. Check for water in oil etc. Its not typical for these dry joint manifolds to leak into the engines, but it will happen eventually. Then you’ve got a whole bunch more problems.
Sorry - meant to say since 2017 not 2007.
 
Ah well then they shouldn’t be that bad. Might have something else clogging like failed impeller parts. Make sure that when they replace the manifolds, they do a good back flush through the system. I would ask them to go ahead and change the water pumps on each engine while they’re at it too.

Good luck with it. Hope it works out. 340’s are great boats!
 
Ah well then they shouldn’t be that bad. Might have something else clogging like failed impeller parts. Make sure that when they replace the manifolds, they do a good back flush through the system. I would ask them to go ahead and change the water pumps on each engine while they’re at it too.

Good luck with it. Hope it works out. 340’s are great boats!

Thanks! We are excited. Good idea on the water pumps - what does that typically run?
 
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Each water pump for an 8.1 will run about $500 for the assembly plus labor. They’re a PITA to change. Not mechanically difficult, but logistically as each one is directly under the engine in that ridiculously tight bilge. I’d expect a mechanic to likely charge you $1500-$2000 to replace both, parts and labor.
 
Each water pump for an 8.1 will run about $500 for the assembly plus labor. They’re a PITA to change. Not mechanically difficult, but logistically as each one is directly under the engine in that ridiculously tight bilge. I’d expect a mechanic to likely charge you $1500-$2000 to replace both, parts and labor.
Thanks!
 

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