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Thread: 2 stroke water pump question

  1. #1

    Default 2 stroke water pump question

    I have an older merc, was at willow yesterday. no water comming out of pee hole. I think my water pump is shot and willl replace the impeller. any other reason no water and only steam would come out? I blew through the ascending copper tube from my lower to my upper and got good flow..I think.....Well let me know what ya'll think


  2. #2


    Is this the first time you fired it up this year? We run motors everytime after running in the salt or silty water (flush them with a motor flusher that hooks up to a garden hose).
    Try the motor flusher and see if you get any flow at all.
    Next, get a 8" or so length of copper wire (12 gauge or whatever will freely enter the water pump stream outlet) and gently (while flushing with fresh water) insert the wire up into the outlet (file or sand the end so it's not sharp). Often there can be debris (sand, mud, etc. in there) and running the wire up in there can dislodge whatever may be there.
    All that being said, it's a good idea to change the water pump impeller every couple seasons (more if you're running shallow in sand and such) as I believe they are typically made out of rubber. The vanes on the impeller get brittle as time goes on (especially if stored out of doors during winter) and can break off or get stuck in the passageway.

  3. #3

    Default Old Merc

    My Dad had an old 7 and 1/2 Merc (I think it was 76' thunder bolt.) What we used to do was wrap the metal bread twist wraps around the motor clamps because we always had to poke the exit hole with one. You would fire it up and nothing would come out, poke poke and a full stream would come out. Very low tech. Hope this is all it is. I had an older 40hp Merc with a bad water impeller. Easy to fix, just don't play with the gear switcher, I learned the hard way (Dumb kid) I had to drop the lower unit a couple times to get it to switch into gear correctly. On that one I had to use bent needle nose pliers to get all of the impeller out of the pump. KB

  4. #4

    Default drill out the pee hole

    Drill out the pee hole to twice the existing diameter, that way sand and grit will pass, but you still get enough backpressure for a bit of a stream to come out v.s. having it just dribble out if you oversize the hole to the full diameter of the hose that discharges through the hole. I learned that one on this Forum...........

  5. #5
    Join Date
    Jan 2007


    Oh the memories...I had a 7.5 thunderbolt too...hunk o poo...finicky heap, I danced the day it died.

    Some mercs have a temp control that don't allow water out the pee hole until the engine is at a certain temperature...I have a 2000 9.9 horse like that and in cold water you stare at it for a good while before it starts to pee....

    But if that's not it...
    Great suggestions here thus far, after doing all the stuff mentioned, and still no go (BTW, I can't stand dropping lower units) if your motor has a thermostat on it that is on the water jacket (usually two bolts)...sometimes the thermostat can trap some stuff in it and like a kitchen sink, it builds up and eventually clogs.

    If you do replace the impeller...the new one probably will have it's vanes pointing straight out, so make note of which way the twist is...that happened to a buddy of mine


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