Manifold & Riser

Discussion in 'General Maintenance/Repair Questions' started by Phasma, Mar 8, 2018.

  1. Phasma

    Phasma Active Member GOLD Sponsor

    199
    Sep 17, 2016
    West Michigan
    2003 360 Sundancer
    Mercruiser 8.1s Horizon
    I rebuilt the starboard engine this winter. Mercruiser 8.1s. I am looking at Sierra manifolds and riser. Freshwater boat. The boat is 15 years old. I only absolutely know it’s history for the last 3 years. It does have a known history of having been in saltwater for its first 3 years in Wilmington NC. After that I have no idea until I bought it 3 years ago. Do I replace both engines manifolds and risers? The set on my starboard engine pressure tested ok. The mechanic is still recommending replacing manifolds and risers due to age. Mercruiser wants stupid money for the set that is why I am considering Sierra. My fun money account is a bit drained at the moment. I am usually better safe than sorry but I expect to have to eventually rebuilt port side. Any input?
     
  2. Michael Mirra

    Michael Mirra Member

    99
    Jan 18, 2017
    Rock Hall, Md
    360 Sundancer 2002
    8.1 Horizon X 2
    You shouldn't have risers, just elbows. The elbows on your boat should be stainless steel and should not need to be replaced.
     
  3. Phasma

    Phasma Active Member GOLD Sponsor

    199
    Sep 17, 2016
    West Michigan
    2003 360 Sundancer
    Mercruiser 8.1s Horizon
    Thanks Michael. That is exactly what I needed to know. If I am replacing the starboard engine manifolds should I automatically replace port engine manifolds at the same time?
     
  4. Michael Mirra

    Michael Mirra Member

    99
    Jan 18, 2017
    Rock Hall, Md
    360 Sundancer 2002
    8.1 Horizon X 2
    I would recommend replacing both, If one is showing signs of failure the other can't be far behind. Replace both and in fresh water you should be worry free for many years
     
  5. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    469
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    I just purchased manifolds for my 8.1's from Michigan Motorz. $460/each plus $100 shipping for all 4. You'll also want to do the gaskets which I got for $43 per. IMO best to replace all 4 and then you're at 'zero' for the set. As others have said your elbows are stainless and should last a loooong time. (I'm in salt and not touching mine)

    Here are the manifolds I purchased:

    http://www.michiganmotorz.com/mercruiser-exhaust-manifold-p-788.html
     
  6. superwa

    superwa Member

    71
    Jul 27, 2013
    Rhode Island
    2001 Sea Ray Sundancer 380
    Mercruiser horizon 8.1S
    Definitely replace. So much more expensive when they fail. My 2001 has aluminum risers that were replaced for stainless. Make sure you have the right stuff. I think for your year there are stainless from factory. If a magnet doesn’t stick with I them, replace.
     
  7. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    1988 Proline Center Console - 90hp Mariner/Mercury
    1969 Boston Whaler
    Twin 8.1 V-drives
    Mike:

    You might want to plan on replacing some of the sensors that are in the manifolds. I have heard that they do not always want to come out nicely. Just a heads up.

    -Kevin
     
    M Prod likes this.
  8. Phasma

    Phasma Active Member GOLD Sponsor

    199
    Sep 17, 2016
    West Michigan
    2003 360 Sundancer
    Mercruiser 8.1s Horizon
    Thanks Mike! That’s what I needed. It looks like I can do a direct replacement of all 4 manifolds for the price of two of the Mercruiser manifolds. This forum has saved me a ton of money. I have zero objection to continue financially supporting Club Searay.
     
  9. Spark600

    Spark600 New Member

    18
    Dec 28, 2013
    Long Island NY
    29' Amber jack with twin 5.7 Mercruiser and V drives transmission
    Kohler Generator
    Mercury dinghy
    29' Amber jack with twin 5.7 Mercruiser and V drives transmission
    I just replaced my manifold witch were cast the part store turned me on to buying the conversion kit for the manifold, the manifold are the same but the kit came with all the sensors, valves, hoses and gaskets for the same price as buying just the manifold.
    Here is the part # for the conversion kit 866178A02
    The kit is used to convert from aluminum manifold to cast manifold.
    I now have 8.1 not 5.7
     
  10. cfd95

    cfd95 Member

    287
    Nov 5, 2013
    Northport Long Island
    2002 310 Sundancer
    350 Horizons
    V Drives
    I would only use mercruiser manifolds.
    Search the forms theres a lot of
    I would only use mercruiser manifolds.
    There's a bunch of threads on this site with problems people have had using aftermarket manifolds and risers.
     
  11. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    469
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Could not agree more! The link I provided is for Mercruiser OEM manifolds from Michigan Motorz.
     
  12. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    469
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Those are actually Mercruiser OEM manifolds for $460! :)
     
  13. Phasma

    Phasma Active Member GOLD Sponsor

    199
    Sep 17, 2016
    West Michigan
    2003 360 Sundancer
    Mercruiser 8.1s Horizon
    I just ordered a set. Thanks guys
     
    M Prod likes this.

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