Exhaust manifold removal on 2003 Sundancer 280

C

C-Lover

New Member
Oct 8, 2015
2
United States
Boat Info
2003 Sundancer 280, twin 4.3L engines
Engines
4.3L Mercruiser w/Alpha one gen 2 outdrives.
I'm a new boater and just discovered that I must replace the exhaust manifolds and elbows on both 4.3L MPI Mercruiser engines on my 2003 Sundancer 280. I have done lots of automobile engine rebuilding but have zero experience with a boat. How does one drain the raw water from the heat exchangers and exhaust manifolds, prior to manifold removal, without sinking the boat?
I am concerned about a siphon effect possibly drawing sea water into the bilge from the exhaust port. Any advice is greatly appreciated.
 
The manifolds have 90* elbows at the bottom with plastic wingnuts to drain them, in your case just remove the hose instead of the plug since you'll be disconnecting. all the water in the elbows and manis will drain out

You won't flood the boat because the elbows have to be above the waterline otherwise your engines would be filled with water. I did both of our motors with the boat floating.

Get two all thread rods with the same thread as the mani bolts and cut it just a little bit longer than the bolts are. You can then replace the two outside bolts with the rods and then remove the inside bolts allowing you to slide the manifold off instead of supporting it while removing them.

Inspect and replace your flappers while you have the elbows off, much easier job that way.

There are lots of mani/elbow replacement threads around but ask away with questions people will be glad to help
 
If you have a closed cooled system with the dry joint, I doubt there is any need to replace your manifolds, there's nothing in them but antifreeze. Engine ser. # would be helpful to see exactly which system you have
 
get 3 inch pvc caps from you local hardware store to plug the exausts tubes using the rubber coupler between the riser and the 90 deg dump.
 
scoflaw said:
If you have a closed cooled system with the dry joint, I doubt there is any need to replace your manifolds, there's nothing in them but antifreeze. Engine ser. # would be helpful to see exactly which system you have
Click to expand...
Dry joint manifolds have water in them
 
There are 2 types of FWC systems. 1/2 and full. The 1/2 which most have just have antifreeze in the block. The full system does block and manifolds. You can check by pulling hose off bottom of manifold and see what comes out. Wish all marine engines had full systems.
 
Shtmetal said:
Dry joint manifolds have water in them
Click to expand...

Dry joint , closed cooled systems have antifreeze in the manifold and the riser. There's a closed gasket between the riser and elbow, so only the elbow sees any water and is the part that becomes corroded.
 
I know for a fact that my 2006 496 merc had a dry joint system and it was just the block that had antifreeze. The exhaust incl manifolds were raw water cooled.
 
Your 5.0 closed cooling is very rare and could have been added aftermarket when new or if factory had the option and could be a full system but many are just 1/2 systems.
 
SAshton said:
Your 5.0 closed cooling is very rare and could have been added aftermarket when new or if factory had the option and could be a full system but many are just 1/2 systems.
Click to expand...

Not rare at all with the 5.0's, It's factory installed, and not a factory special order, part of my engine ID #. For some reason only the small blocks got it.
Without the OP posting up his engine number, who knows what system he has.
 
SAshton said:
I know for a fact that my 2006 496 merc had a dry joint system and it was just the block that had antifreeze. The exhaust incl manifolds were raw water cooled.
Click to expand...

That is the set up that I have, and as others have stated, it's what is know as a half system.
A full system has anti-freeze in the manifolds.
 
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