Risers Manifolds Elbows - Mercruiser 5.0 MPI

CaneCorso

Member
Jan 5, 2017
56
Chattanooga, TN
Boat Info
2006 Sea Ray 290 Sundancer
Engines
Twin 5.0L MPI w/Bravo IIIs
Good morning,

I bought my boat roughly 1.5 yrs ago from (from saltwater, now in freshwater) and I am needing to change the manifolds, risers, elbows due to surface rust (it is not currently running hot). I am mildly adequate at maintenance, last year I managed to do a full tune up. I have scoured the internet at this forum to find a step by step DIY for this job, but have had little luck, and before I drop $4K + on parts I want to be sure I can tackle this job. From what I read, it is straightforward, just heavy parts but mostly just bolt-ons. Can someone who has do this chime in on my understanding?

1. 2-3 days prior – PB Blaster on bolts to ensure they don’t break when removing

2. Drain water from blue plug (on manifolds?)

3. Disconnect exhaust port clamps/remove

4. Remove four bolts from riser and remove

5. Remove four bolts from manifold and remove

6. Clean areas where gaskets will go, and apply silicone around parts with waterflow, reinstall.

I’ll be replacing with all OEM and all new gaskets. Also removing something called a T-fitting at the bottom of the manifold. I have a pic and its confusing me, because it almost looks like there are two risers on top of each other, when compared to the 6” riser I was told that likely goes with my engine. Does this pic tell you anything?

Am I missing anything, other than be prepared for some heavy parts?

oa0oie.jpg
 
Looks like you have 2 3inch spaces on top of each other... But in regards to your question it is easy to change even if you do the spaces.... Which i would do them.. Are those org from factory? Did you buy the boat new? If it is then put the spaces back in... I think thats what they are talking about when they say 6inch rises....
 
the parts are heavy.. have help or... elbows and risers not too bad solo but for manifolds i took a 2x4 across the deck, used a ratchet strap to put a little tension holding up, removed bolts and suspended from strip to remove...even better for installation and aligning bolts....
 
Looks like you have 2 3inch spaces on top of each other... But in regards to your question it is easy to change even if you do the spaces.... Which i would do them.. Are those org from factory? Did you buy the boat new? If it is then put the spaces back in... I think thats what they are talking about when they say 6inch rises....

Not sure if they are from factory....only had boat 1.5 yrs. both pieces are different sizes, the top is roughly half the size of the other. I tool a photos of the stamped number and showed to the parts dept at the marina and they said I need the six inch riser. The numbers are 864531-C and 865944-C.
 
the parts are heavy.. have help or... elbows and risers not too bad solo but for manifolds i took a 2x4 across the deck, used a ratchet strap to put a little tension holding up, removed bolts and suspended from strip to remove...even better for installation and aligning bolts....

thanks. I will be by myself unfortunately. I was going to find a similar size bolt and cut off the head and threads to feed through the manifold holes when i am reinstalling just so it can hold it in place.
 
Another trick when installing the new manifolds - get some threaded rod or bolts the same size as the ones that hold the manifold on and cut the heads off. Put two of them in, slide the manifold on, this will hold it in place while you install the other bolts, then you can replace the cut off bolts with the permanent ones. Keeps you from having to try and hold the heavy manifold and thread the bolts in. The strap idea Happy Daze mentioned would work just as well. Be careful and patient, if you snap any of the bolts, the job becomes much harder.
 
Go to Harbor Freight and get yourself a 3/8" drive, battery powered impact gun. It makes removal/installation of the bolts go much faster. Nothing worse than using a socket/ratchet to remove these bolts by hand.
 
Another trick when installing the new manifolds - get some threaded rod or bolts the same size as the ones that hold the manifold on and cut the heads off. Put two of them in, slide the manifold on, this will hold it in place while you install the other bolts, then you can replace the cut off bolts with the permanent ones. Keeps you from having to try and hold the heavy manifold and thread the bolts in. The strap idea Happy Daze mentioned would work just as well. Be careful and patient, if you snap any of the bolts, the job becomes much harder.

This is the way I did it, just try and make the stud the right length using your new manifolds as a guide. The problem is with engines that close on the inboard sides is if the stud is too short you can't grab it but if it's too long you won't clear the other manifold when removing it.
 
I supposedly have a 1.7” riser on top of a 3” one. Some thing doesn’t seem right with this setup but the photo clearly shows it.
 
I supposedly have a 1.7” riser on top of a 3” one. Some thing doesn’t seem right with this setup but the photo clearly shows it.

Any luck looking up your serial numbers for parts diagrams to see what OEM would have been?
 
Any luck looking up your serial numbers for parts diagrams to see what OEM would have been?

I have tried but maybe I’m looking in the wrong place... every place has options for different sizes. My engine SNs are 0W625775 and 0W374103 if someone can answer this.
 
According to Mercury, one engine I have shows OEM from factory with a 6" riser and the other at 4.7". He said sometimes this happens and recommended going with 6" as long as I have the clearance. That's what I am going to try, so hopefully my engine hatch will close, fingers crossed (not sure why it wouldn't if it was factory on one of them.
 
Those look like dry joint risers.
They are more expensive than conventional risers.
Thats a lot of spacers.
I paid 280.00 a pair for the 3 inch spacers for each motors.
Do you have the Catalyst exhaust on those motors?
That might be the reason for the high price quotes you are getting.
 
No idea how I would know that; I am going to go with what Mercury rep told the parts section at the marina, which was to go with the 6" as long as I have the clearance. He said you can always go larger, but not smaller....hope that is sound advice. The larger quote for parts was due to them originally saying i need sets of 1.7 and 3 inch risers. Now i am back down to roughly $5k with gaskets and new bolts, etc.
 

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