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  1. #1

    Default No water from telltale at high revs

    Hi all, first time poster.

    I've a late 80's 40hp Classic with a serial number between C159200 - C221499.

    When idling it has a good strong flow of water out the telltale outlet. However, from anywhere beyond 1/4 throttle up to full throttle the water flow begins to waver, then disappear and then within seconds it begins to steam and hiss. Bringing it right back to idle sees the resumption of a good strong water flow out the telltale outlet within seconds.

    Now, when it first happened a few years back I replaced the impeller, and it did it again. I then thought bugger it, and left it in the shed for a few years. I dusted it off last weekend and the same thing was still happening. So, I'm going to try a fresh impeller again, but is there anything else I should be considering?

    The confusing thing is that at low revs it pumps well, but at high revs, its almost like its being starved of water.

    Any advice?

    DMC73

  2. #2
    Join Date
    Jun 2013
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    Duluth Mn
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    Default Re: No water from telltale at high revs

    Welcome.
    I've heard of this before, but never ran into the problem directly, myself. Perhaps at high speed we are leaking air/exhaust into the water jacket. I'm thinking we have to remove the exhaust cover, but let's appeal to another tech.
    Last edited by timguy; 01-19-2022 at 12:28 AM. Reason: Typo

  3. #3
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    Default Re: No water from telltale at high revs

    Is this with it running is a test bucket or with boat off the trailer in the lake ?

  4. #4
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    Default Re: No water from telltale at high revs

    Quote Originally Posted by racerone View Post
    Is this with it running is a test bucket or with boat off the trailer in the lake ?
    Good question.....does make a difference.

  5. #5
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    Default Re: No water from telltale at high revs

    Many folks are still not aware of the fact that the water level in a test bucket needs to be 8" above the impeller.---Pumps are not self priming.------And when you rev up a motor in a test bucket there are 101 exhaust bubbles in the water,.----Pumps do nut pump air very well.------I can not see , feel or hear this motor described in post #1.

  6. #6
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    Default Re: No water from telltale at high revs

    Seems he has had an ongoing problem, so I assumed he is in the water. There is something I remember regarding this symptom. Pretty sure it involves the exhaust cover. Not everyone knows of it.

  7. #7

    Default Re: No water from telltale at high revs

    The motor could be too high on the transom or tilted too far out, I have tested both scenarios.
    There could also be a problem with the hull, deformed somehow - since this has happened all the time these are my observations.
    Click image for larger version. 

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    Last edited by Quicksilver; 01-19-2022 at 02:37 PM.

  8. #8

    Default Re: No water from telltale at high revs

    Instead of a new impeller get the entire water pump kit and replace it all. It doesn’t take much warpage of a base plate or a worn gasket to decrease water pump performance. By doing so you will eliminate the water pump as the problem, if you still have issues. When you have the lower unit off have a real good look at the water tube and the water pump discharge. Does it look like the water pump discharge will mate with the water tube? I’m not familiar with your engine but often there is a rubber grommet of sorts that will mate the water tube to the water pump. A 40 year old engine the grommet may have deteriorated. A service manual is always a help, parts diagrams will also give you an idea of what to look for.

  9. #9

    Default Re: No water from telltale at high revs

    Quote Originally Posted by Texasmark View Post
    Good question.....does make a difference.
    Hi, thanks for the response. Each time its been running in a lake, so not in a bucket.

  10. #10

    Default Re: No water from telltale at high revs

    Quote Originally Posted by Quicksilver View Post
    The motor could be too high on the transom or tilted too far out, I have tested both scenarios.
    There could also be a problem with the hull, deformed somehow - since this has happened all the time these are my observations.
    Click image for larger version. 

Name:	I6-testing.jpg 
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ID:	28246
    Hi, thanks for the feedback. Transom has a cut out with a lower middle section. The top of this lower section is 1ft above the water line. It's a long shaft, so there is plenty of the leg in the water. The leg is trimmed down as low as it goes, and I've tried running it a little higher in the event that there is an air pocket being created at speed, but the same thing happens.

  11. #11

    Default Re: No water from telltale at high revs

    Quote Originally Posted by William01 View Post
    Instead of a new impeller get the entire water pump kit and replace it all. It doesnít take much warpage of a base plate or a worn gasket to decrease water pump performance. By doing so you will eliminate the water pump as the problem, if you still have issues. When you have the lower unit off have a real good look at the water tube and the water pump discharge. Does it look like the water pump discharge will mate with the water tube? Iím not familiar with your engine but often there is a rubber grommet of sorts that will mate the water tube to the water pump. A 40 year old engine the grommet may have deteriorated. A service manual is always a help, parts diagrams will also give you an idea of what to look for.
    Thanks for your feedback. I'll place an order for a new water pump kit this afternoon. In terms of the water tube there is a rubber grommet on the bottom of it that I replaced it last time I had the leg off. But, out of curiosity, I might actually remove the driveshaft housing assembly and have a look at the upper end where they tube sides into the bottom of the engine. Its a little hard to see up the inside of the housing to check the condition of the female insert and the top rubber grommet.

    Again, if anyone has had this exact same issue in the past, I'd appreciate your views.

  12. #12
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    Default Re: No water from telltale at high revs

    So your plenty deep in the water. By the way, is this a saltwater motor? I'm sure you have checked the water supply opening and suction side all the way to the pump. I don't remember if the screens can be reversed on these. I'll see if I can get some details on my earlier suspicion. See post #2 and post #6. I really thought Pappy, Quicksilver, Jeff, Mr. Scott, or Racer would know. I'm primarily from the Johnson/Evinrude side, although I play a little with Mercs too.
    Last edited by timguy; 01-20-2022 at 12:56 AM. Reason: Typo

  13. #13

    Default Re: No water from telltale at high revs

    It's a salt water motor. I'll remove the plastic filter, but from memory when I last replaced the impeller prior to lockdown here in Aus, I flushed it to check for buildup. I do however, run the motor in fresh water with a set of muffs after each outing and again in a large tank I have at the garage. But I'll do it again when I take the leg off. Thanks again for your feedback, and I'd appreciate the additional info if you can lay your hands on it.

  14. #14
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    Default Re: No water from telltale at high revs

    Okay, one phone call tomorrow. It's midnight here. I've been through Queensland, got friends there. Australia rocks, brother.

  15. #15
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    Default Re: No water from telltale at high revs

    Remove lower unit.----Look up into exhaust tuner.----Check for blockage ( carbon ) restricting exhaust.

  16. #16

    Default Re: No water from telltale at high revs

    Thanks racerone, I'll add that to the list this weekend.

    Many thanks for the feedback.

  17. #17
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    Default Re: No water from telltale at high revs

    Sorry didn't make that call, but will try to get through tomorrow. We are at opposite side of the clock.

  18. #18

    Default Re: No water from telltale at high revs


  19. #19

    Default Re: No water from telltale at high revs

    https://youtu.be/joEQChcZl2A

    You will have to copy and paste

  20. #20
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    Default Re: No water from telltale at high revs

    Not sure why the above video was posted.-----William01----You are aware that this motor being discussed in post #1 does NOT have a head gasket !

  21. #21

    Default Re: No water from telltale at high revs

    Quote Originally Posted by racerone View Post
    Not sure why the above video was posted.-----William01----You are aware that this motor being discussed in post #1 does NOT have a head gasket !
    I do now. My thought was the video gives some good information should the problem not be cured with a water pump replacement.

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