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Changed water pump for my 1st time V-6 Merc 200 EFI, no water flow. Most likely thing I got wrong?

RangermanRangerman MemberTitusville FLPosts: 86 Deckhand

I installed a water pump kit for my first time on a 1996 Merc 200 EFI.  Before installing the kit, for the past 14 months since I bought the boat water flowed just fine.  I'm mechanically inclined, but obviously got something wrong.  I ran the engine on water muffs, which I have done many times before.  I was waiting for the peeing to start and it seemed like it was taking a long time.  Then the overheat alarm went off so I shut it down.  I know the alarm was not a lack of oil because this engine was converted to pre-mix with the block off kit long before I bought it.

What is the most likely thing or things I could have gotten wrong that it will not flow water?  Knowing that in advance may help me in taking the water pump assembly apart to diagnose it.  I was certain I got the key in the right place.  I rotated the drive shaft clockwise as I slowly pushed the pump housing on to the impeller.  I followed the steps in my shop manual verbatim.

Thank you


  • kmagnusskmagnuss Senior Member Englewood, FLPosts: 3,237 Captain
    Did you put the cog back in?  The little metal half moon looking piece that makes the impeller spin when the shaft spins?  (it has a name... it's not cog).

    Also... are you sure you have the impeller twisted the correct way?  If it's backwards it usually won't work.

    Tarpon... everything else is just bait.
    Captain Keith - Crooked Rod Charters
  • kmagnusskmagnuss Senior Member Englewood, FLPosts: 3,237 Captain
    Here is the "cog"... aka Woodruff Key
    Tarpon... everything else is just bait.
    Captain Keith - Crooked Rod Charters
  • kmagnusskmagnuss Senior Member Englewood, FLPosts: 3,237 Captain

    Tarpon... everything else is just bait.
    Captain Keith - Crooked Rod Charters
  • RangermanRangerman Member Titusville FLPosts: 86 Deckhand
    Yes I put the metal cog or key on just the way it says in the shop manual and how I saw it done on YouTube videos.  I stuck it to the flat portion of the drive shaft with some grease and slid the impeller with the slot lining up with the key center.  I rotated the drive shaft clockwise when sliding the pump cover over the impeller just as the shop manual said.
  • StankBaitStankBait Senior Member JacksonvillePosts: 422 Deckhand
    My guess is that the tube from pump did not line up into passage. Sometimes it takes two people. One to hold the lower unit and the other to stick fingers in there to align the tube. It can slip over, thus no water to upper part.
  • Tony RomaTony Roma Senior Member Posts: 3,854 Captain
    ^^^this, which is a good thing,then you don’t have to take the entire pump off again. While you got the lower unit off try to run some compressed are back through the tell tail just to make sure nothing got lodged up in the main water intake, then have someone help you line the lower unit feed to the main feed. Good luck and great job keeping that 20 year old motor going!
  • billybobbillybob Senior Member Walnutgrove,GaPosts: 926 Officer
    Oring in housing.  If it came out while closing it will let it suck air while on muffs. But would work well while submerged.  More than likely impeller is toast now.  I did not see this type oring in parts picture 
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