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  1. #1
    Join Date
    Sep 2018
    Location
    London
    Posts
    86

    Default Mercury 3.3 pumps little water and other issue

    Hi,
    my Mercury 3.3 telltale water flow is very limited - only drops of water are coming off, it used to be solid stream. It happened recently, as I used it just few time for like 500 yards tender commute. I might hit ground with it - mud, gravel and so on - maybe it got stucked in waterways?

    I was flushing it yesterday (in small bucket), and I noticed it spits water through 2 small holes in front, few inches above propeller shaft.
    There is not a lot resources on the web, especially no repair manual, but I read some horror stories about resembling gear linkage - in case I would need to change impeller.
    If I will lift from the water and there is water coming off the engine - is it sign it works fine?
    In worst case, how long I can have engine running before there will be any trouble?

    There is second thing that happened yesterday - when starting for flushing I heard loud thud - though it was bucket cracking - turns out it was rubber cover of inspection hole that was blown away - I wonder how come there was pressure to make it happen?

    Besides, engine works fine, starts almost immediately, and is stable on low revs.

  2. #2
    Join Date
    Apr 2016
    Posts
    186

    Default Re: Mercury 3.3 pumps little water and other issue

    It could just be the telltale that is bunged up. Try poking a thin piece of wire into the hole and see if this cures it - it only takes a few salt crystals to stop the flow. Worth trying before taking more complicated steps!

  3. #3
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,896

    Default Re: Mercury 3.3 pumps little water and other issue

    Another problem that can block the telltale flow is salts in the cylinder head passages. Very easy to remove the head and clean them out.
    Answers to some technical queries at new website http://coxeng.co.uk

  4. #4
    Join Date
    Jun 2013
    Posts
    3,417

    Default Re: Mercury 3.3 pumps little water and other issue

    Those rubber gear link covers fly off all the time. I have lost three or four. Last time I bought an aftermarket one on eBay for less than an original Mercury part and it has stayed on ever since. The aftermarket one was a much tighter fit in the hole. I don't know why they come off, but suspect it is some kind of 'backfire' that pressurizes the exhaust.
    If found in the Brexit forum, please return to the real world.

  5. #5
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,538

    Default Re: Mercury 3.3 pumps little water and other issue

    Quote Originally Posted by slawosz View Post
    Hi,
    my Mercury 3.3 telltale water flow is very limited - only drops of water are coming off, it used to be solid stream. It happened recently, as I used it just few time for like 500 yards tender commute. I might hit ground with it - mud, gravel and so on - maybe it got stucked in waterways?

    I was flushing it yesterday (in small bucket), and I noticed it spits water through 2 small holes in front, few inches above propeller shaft.
    There is not a lot resources on the web, especially no repair manual, but I read some horror stories about resembling gear linkage - in case I would need to change impeller.
    If I will lift from the water and there is water coming off the engine - is it sign it works fine?
    In worst case, how long I can have engine running before there will be any trouble?

    There is second thing that happened yesterday - when starting for flushing I heard loud thud - though it was bucket cracking - turns out it was rubber cover of inspection hole that was blown away - I wonder how come there was pressure to make it happen?

    Besides, engine works fine, starts almost immediately, and is stable on low revs.
    As suggested check that the telltale itself is not blocked. If it is actually overheating in use then the water passages may be blocked as Vyv suggests or it may need a new water pump impeller.

    Here is the Service manual http://www.boatinfo.no/lib/mercury/m...5-3-33.html#/0

    A small bucket is no good for flushing. The water must be deep enough cover the water pump ( on top of the gear case in all engines with a neutral gear position although often " behind" the prop in modern fixed drive engines. Insufficient water depth combined with the turbulence cased by the exhaust gases may be the cause of your lack of water flow.

    Cannot explain the sudden expulsion of the rubber plug . A back fire of unburnt fuel and air in the exhaust perhaps ????
    Last edited by VicS; 15-07-19 at 09:45.

  6. #6
    Join Date
    Sep 2018
    Location
    London
    Posts
    86

    Default Re: Mercury 3.3 pumps little water and other issue

    Thanks for answers. This forum is excellent!
    I am thinking about using guitar string, will give a try.

    Quote Originally Posted by VicS View Post
    A small bucket is no good for flushing. The water must be deep enough cover the water pump ( on top of the gear case in all engines with a neutral gear position although often " behind" the prop in modern fixed drive engines. Insufficient water depth combined with the turbulence cased by the exhaust gases may be the cause of your lack of water flow.
    Water is deep enough to cover all holes and engine is tilted so all holes are submerged. The think is its small boat and I need to carry entire water on my tender, so the smaller bucket the better. I was thinking about making something for close fit, but haven't manage find time...

  7. #7
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,538

    Default Re: Mercury 3.3 pumps little water and other issue

    Quote Originally Posted by slawosz View Post
    Thanks for answers. This forum is excellent!
    I am thinking about using guitar string, will give a try.



    Water is deep enough to cover all holes and engine is tilted so all holes are submerged. The think is its small boat and I need to carry entire water on my tender, so the smaller bucket the better. I was thinking about making something for close fit, but haven't manage find time...
    The water pump should be submerged. This means that the water should be deep enough to be well above the gearcase to driveshaft housing, (( by a couple of inches is the usual recommendation ) This is unlikely to be the case with a "small bucket"....

  8. #8
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,538

    Default Re: Mercury 3.3 pumps little water and other issue

    Hve you seen the link to the service manual which I added to #5?

  9. #9
    Join Date
    Sep 2018
    Location
    London
    Posts
    86

    Default Re: Mercury 3.3 pumps little water and other issue

    Quote Originally Posted by VicS View Post
    Hve you seen the link to the service manual which I added to #5?
    Yes. It is great!

    Quote Originally Posted by VicS View Post
    The water pump should be submerged. This means that the water should be deep enough to be well above the gearcase to driveshaft housing, (( by a couple of inches is the usual recommendation ) This is unlikely to be the case with a "small bucket"....
    Well, relatively small - the one that is used with mop, holds around 2 gallons of water.

  10. #10
    Join Date
    Jan 2011
    Posts
    5,735

    Default Re: Mercury 3.3 pumps little water and other issue

    Stick an airline against the pee hole and give it a good blast.

    Always works for me.

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