8.1 Horizons Replacing Water Pumps and Manifolds

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by M Prod, Mar 6, 2018.

  1. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Hey all,

    Since we purchased our 340DA last October, I've always gotten different water pressure readings as well as temps from both engines. Port engine runs slightly warmer than starboard and has a significantly lower water pressure though neither engine is anywhere near overheating. (I've swapped out sensors and checked temps at the manifolds to verify this). In any case, seeing as I have no idea how old the current manifolds on the boat are (I can only assume they are original as well as water pumps), figured what's the harm in replacing everything other than a dent in my wallet. At least my wallet won't be emptied from having to re-power due to a manifold failure. Anyway, hopefully this will address the discrepancies once and for all, and at the very least it will put my manifolds and water pumps at "zero" for my peace of mind as we embark on some serious cruising this upcoming season.

    Now after making this decision, I went to a mechanic that a friend of mine recommended and asked him to give me a quote. New manifolds and water pumps on both engines installed were going to run me in the neighbourhood of $8000CAD. $1000 per manifold "set" and $1000 for each water pump=$6000 for parts alone. Now me being the somewhat thrifty guy I am, decided that was crazy and went ahead and did some research on my own. I ended up buying 4 manifold sets from Michigan Motorz, and 2 water pumps at wholesale from a distributor up here. Total cost to me: $3300CAD. A significant savings. Everything should arrive Monday, and I plan to do the install myself next Thursday. Having been a boater for around 3 years, I've yet to find a truly honest mechanic. (no offense mechanics ...maybe it's where I live) And so I continue to learn and teach myself how to work on my boat which I continue to find very rewarding. It's not easy and can be more time consuming ...but I find if I take it step by step and go slow, I can usually get the job done barring an engine rebuild or something more major like that. Anyway just wanted to share, and I'll let you know how the install goes ...and if it solves the pressure and temp discrepancies.
     
  2. rmlsll

    rmlsll Member

    143
    Oct 11, 2009
    Saugatuck MI / Cape Coral FL
    340 Sundancer 2004 /
    240 Sundeck 2007 /
    10' Zodiac
    Twin 8.1 merc,. V-Drive /
    5.0 merc., bravo 3
    make a couple of threaded rod studs to take the place of the manifold bolts. Slide the new gaskets on the studs and then the manifolds. Will line up things so you can get some bolts started.
     
  3. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Great advice. Thanks, and will do!
     
  4. superwa

    superwa Member

    71
    Jul 27, 2013
    Rhode Island
    2001 Sea Ray Sundancer 380
    Mercruiser horizon 8.1S
    If they are original they are way overdue. Glad you are getting them done. Post some photos of the work? Also a question from your profile photo. What’s that rod that’s almost horizontal? Attaching a photo of what my manifolds looked like after 9 years. Will probably do 5 next time.
     

    Attached Files:

  5. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Yikes that's nasty. Mine probably look about the same. I will definitely post photos of mine and you're right ...they are way overdue. Engines run strong and no water in oil (yet) so need to keep it that way.

    That's an electric downrigger in my profile photo used for Salmon fishing. It carries an 18lb weight on a steel cable which you attach the fishing line to via release clip. I then use the downrigger to lower the line to a specified depth like 180ft this time of year. When a fish is on, the release clip releases the line from the downrigger so you can reel it in. They're really common up here and the only way to really fish for Salmon.
     
  6. superwa

    superwa Member

    71
    Jul 27, 2013
    Rhode Island
    2001 Sea Ray Sundancer 380
    Mercruiser horizon 8.1S
    Neat stuff!
     
  7. Strecker25

    Strecker25 Well-Known Member

    Nov 20, 2014
    Rochester, NY
    1998 290 Sundancer
    Twin 5.7EFI/Alphas, Kohler 4kw
    Definitely due if they’re original. The OEM manifolds were likely aluminum so if you’re curious if they’re original throw a magnet on them when you’re at the boat again.

    When you say “set” did you also buy the elbows? They should be stainless on your motor and I’m pretty sure most folks reuse them. Of course, replacing them can’t hurt. Make sure you replace all the gaskets with new and torque to spec
     
  8. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    New manifolds and gaskets. Yes sir risers 'should' be fine as they are stainless. I'll be sure to have a look once I take things apart. The current manifolds are cast iron. Had they been aluminum I'm sure the engines would have been ruined a long time ago. I'm not certain, but I believe that Mercury had moved away from the aluminum manifolds on the 8.1's by 2005, but then again I may be wrong. If they are original, the boat was moored in a river most of it's life (mostly fresh but also brackish water and cruised in salt) and that may be the only thing that's saved it thus far. That in addition to the integrated fresh water flush system which I'm hoping the previous owner made use of. In any case, I can't wait to see what the insides of these things look like. I'm sure I'll be happy I made the switch. :)
     
  9. GCHOG

    GCHOG Member

    103
    Mar 25, 2016
    Bass River, Viking Marina, South Jersey
    2006 Sea Ray 260 Sundancer
    6.2 Bravo III
    +1 on what rmlsll said, great tip. Just make sure you make the threaded rod studs about 2" longer than the manifold bolts so you can grab them with pliers or vise-grips to remove them so you can put the bolts in place. oh, and put a little "never-seize" on the bolts and torque to spec. oh , 1 last thing, take a pic of your serpentine belt before removal, it'll save a little frustration figuring out how it goes around each pulley for installation.
     
  10. sbw1

    sbw1 Well-Known Member

    Oct 10, 2006
    West Michigan
    This is listed in my signature
    This is listed in my signature
    After hearing about Merc water pumps and how they hold up, I'm wondering if any Merc owners have looked the feasibility of swapping the Crusader pumps in their place. Crusader uses no plastic. The housings are stainless steel and the impellers are bronze. At least in fresh water, they seems to last forever on 8.1s. If this is easily done, people would probably be talking about it. Anyway, just wondering.
     
  11. Strecker25

    Strecker25 Well-Known Member

    Nov 20, 2014
    Rochester, NY
    1998 290 Sundancer
    Twin 5.7EFI/Alphas, Kohler 4kw
    This, or in my case the inside manifolds were so close together if I made the stud long I wouldn't have been able to get it out so I dremeled a small wedge slot in the end that a flathead screwdriver was able to pull it out.
     
  12. Kimpa

    Kimpa Member

    30
    Jan 9, 2017
    Sweden
    340 Sundancer 2000
    7.4 Mpi V-drives x2
    Hello,

    I am also going to change all of the manifolds and risers this season, are you going to change all of the "rubber hose" aswell? im my case the are quite hard and solid and im considering of just cut them open to have the demounting a little easyer.

    / Kim
     
  13. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    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’ll have a look inside the hoses when I remove the manifolds to see if they need replacing, but things look (and feel) pretty good on my end anyway. I wasn’t planning on replacing them but I’ll let you know if it was needed. Thursday is the install day.
     
  14. mnm99

    mnm99 Well-Known Member

    Oct 2, 2015
    Long Island
    2004 340 SeaRay Sundancer
    Twin 8.1 Merc
    FullSizeRender 1 (1).jpg Make sure you go over all those hose clamps once your done. I did my manifolds at the beginning of 2017. I was just in the boat doing some work and a few clamps were real loose. I know they were tight before, so just go over them all once and a while.
     
    Kimpa likes this.
  15. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    Great advice will do! That looks familiar. :) I'm still dreading the day when I need to replace shaft seals. Not sure how I'm going to get down between those engines and still be able to move.
     
  16. Kimpa

    Kimpa Member

    30
    Jan 9, 2017
    Sweden
    340 Sundancer 2000
    7.4 Mpi V-drives x2
    I understand, soon then, great!

    If you look at mnm99's picture above, is it easier to start with loosening the clamps everywhere and all small hoses then unscrew one of the manifolds with the riser still mounted and then pull off the "hose" backwards if you know how i mean.

    Can't wait for pictures of your installation.

    / Kim
     
  17. Tomco

    Tomco Member

    160
    Aug 16, 2012
    Ottawa
    2003.5 Sundancer 340; Raymarine RL70
    496 MerCruiser w/Bravo III Drives
    Was also considering replacing the hoses as part of the on-going maintenance. Is there a engine 'hose kit' that can be purchased or are they ordered one at a time?
     
  18. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    Oct 6, 2017
    North Vancouver, BC
    2005 Sundancer 340
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine Electronics
    8.1 Horizons /V Drives
    First off, this is a really difficult job. Much more so than it looks on paper. We did not finish yesterday and managed to get through about 80% of the job. Managed to replace both water pumps, and nearly 3 out of 4 manifolds. Port engine is done, and starboard engine port side manifold is halfway ..haven't touched the starboard side manifold on starboard engine. Will finish Tuesday most likely. Both water pumps were badly scored and likely originals, so I'm really glad I replaced both. (sorry didn't get photos of water pumps ..but they were bad). The housing that attaches to the water pump was also pretty scored, so I used a belt sander to sand that down smooth and reattached. The manifolds themselves were definitely corroded (but probably would have lasted a little longer) ...regardless happy they are new. I think they must have been replaced at some point and were likely not original. We also painted all the new manifolds with a couple of coats of black anti rust paint which I recommend doing before install. Also ended up buying 6ft of hosing and replaced a few pretty worn hoses. But not all as some of the hosing looked pretty new. Here's a few photos ..

    Insides of old port engine manifolds:

    IMG_1034.jpg

    IMG_1036.jpg

    Old manifold and gasket

    IMG_1035.jpg

    New manifold going in on starboard engine (I'll clean the bilge once job is done! :))

    IMG_1039.jpg
     
    Last edited: Mar 16, 2018
  19. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    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 don't know about an engine hose kit, but the hoses that attach to the manifolds on the 8.1's are 19mm diameter as measured from inside (3/4 inch). You can get a length of as much as you would need at any marine store, and then cut from that length for each individual application.
     
  20. M Prod

    M Prod Active Member SILVER Sponsor GOLD Sponsor

    468
    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 did end up getting a picture of the inside of one of the old water pumps today. Yup, it was time.

    IMG_1050.jpg
     

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