QD19 Overheat Question – Update

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  • beerman57


    Replies: 596
    Topics: 126
    #18786

    Thanks a ton for taking the time to check these things out for me. Thanks to everyone who has been trying to help me resolve this problem. I guess I’ll put it on the back burner for now, wait to see if Garry can find anything in the service bulletins. Like I said, I never checked the cyl. head after being up on plane, but it runs too good and pumps lots of water. It seems like it’s something after the water and exhaust leaves the P/H.


    chris-p


    Replies: 2456
    Topics: 153
    #18788

    Did you try removing the plate to ensure the port is open that was mentioned? I would find it hard to believe it could get plugged, it is actually pretty big, but you never know. If it was plugged, the exhaust would back up as mentioned.


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #18795

    Yes, the early 60s QD exhaust hsg I was looking at had a dividing wall that extended much farther down between the exhaust chamber and shift linkage cavity.
    The only other thought I had was when I remembered that some newer style engines actually have a very small pinhole towards the top of the intake water tube allowing a fine spray into the exhaust housing. I know the QD has a very short water tube, but perhaps there is a little bleed hole in the aluminum casting that water flows through on top of the water tube. Perhaps Mumbles could try plugging the bottom of the water tube of his 58 QD hsg, then slowly filling the intake water tube from the top of the exhaust housing to see if water leaks out anywhere in between.


    chris-p


    Replies: 2456
    Topics: 153
    #18796

    Well I opened up a few motors, and pulled a bunch of parts mids I have to investigate.

    I could not find any with the modified drilled hole. I could see how that could work though. If you shot a drill bit on a downward angle, through the water intake tube, almost towards the shift handle, it would "mist" cooling water in that area. Now the downfall of that would be if your lower crank seal failed, the water would "climb" the drive shaft and enter the powerhead easier. If the seal is good, which I assume you would change if you had the powerhead pulled anyways, should not be a problem

    The real question is though, why is it heating up there?? I have never seen that before. Only thing I can think of is exhaust is building there, and not getting siphoned out through the snout until you get on plane.

    Can you physical SEE the exhaust mixed in with the cooling water when puttering at an idle?

    Sorry, Im at a loss, other than if that passage is plugged somehow beneath the plate into the other chamber.


    beerman57


    Replies: 596
    Topics: 126
    #18801

    The spent water relief hole into the mid/exhaust cavity isn’t plugged. It seems strange that after even a short run on plane the shift lever cools right down, but the upper mid doesn’t. it’s not even like the motor sits low in the water at idle, making it hard for the exhaust to get down the mid.
    Chris, seems to me – why drill a hole in the water tube when a hole in the spent water tube does the same thing, without affecting the incoming water.
    The relief hole in the spent water cavity is more like an overflow, it comes out inside the mid at the same level as the spent water exits to the outside, about 7.5" above the mid & L/U mating surface. So any exhaust has to travel back up the relief hole to mix with the spent water.
    I do know someone at a marina who might have access to the OMC service bulletins. You know what really sucks about all this, I wanted to have these two 10hp motors done about a month ago, before I put my MK50 on the boat, since it’s all I can do to lift it.


    beerman57


    Replies: 596
    Topics: 126
    #18802

    You know what Chris, something you said about the exhaust building up. You know how when you get some weeds around the L/U and that causes you to be able to hear the exhaust. I keep getting that, so I slow down, shift to reverse to clear the weeds, but there is never anything there. That screen in the snout water pickup isn’t perfect, but doesn’t appear bad enough to cause a problem and isn’t clogged. Shouldn’t be a problem at idle anyway. Just something else to ponder.


    jeff-register

    US Member - 2 Years
    Replies: 1564
    Topics: 54
    #18814

    Guys,
    This may or may not apply. All of my Mercury motors I’ve been into have a pin hole in the copper water line. I believe it has a dual purpose.
    The first application is so after running the motor, the water line in is still full of water. The pin hole allows the block to drain water from the cooling system to protect the powerhead from water intrusion.
    The second app is to spray a small amount to help cool the exhaust cavity while running.
    Robert,
    I believe we still are missing something & I bet it’s simple as we are digging so deep. Seems Johnson was aware of this problem as changes were made very soon once into production. I believe the solution is in the service bulletin & drilling out an extra water output somewhere safe from the D-shaft splines or an additional collar was added to protect the D-shaft. Robert, I know about the Merc 4 cylinder motors. My Mark 30 is very hard to lift for this old guy.
    Jeff


    Mumbles


    Replies: 5764
    Topics: 298
    #18819

    Later OMC motors had the pin hole in the tube to fill the inner exhaust housing with water. This helped to keep the noise down, especially from those three cylinder loop charged motors.

    If you look at the ’58 QD exhaust housing, you will see that the drive shaft and its spline area are in a sealed tube which is separate from the exhaust chamber.

    Before doing anything drastic like drilling a hole into the cooling water passage, please try to find the service bulletin describing this issue. It has to be out there somewhere. Wedgie might even have it in his stash. If you do decide to drill a small hole, I’m guessing it would go in the area marked by the red arrows.


    beerman57


    Replies: 596
    Topics: 126
    #18823

    I’ve been searching service bulletins. Fiberglassics has a list of Evinrude bulletins, but I don’t see any way to read them. Wouldn’t an Evinrude have the same problem? I read ALL the titles and didn’t see one that would definitely be it. On the Fiberglassics page it says Johnson put their bulletins in the service manuals.


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #18824

    Yeah, I would think that would be the best location as well. Just make sure the hole is angled downward to ensure the water is not spraying directly into the shift linkage. You could always seal the hole up again easily with marine tex if it didn’t work out. I’ll bet you wouldn’t be having a problem if the wall between the exhaust and shift linkage was deeper, like on later models.
    I’m guessing a 1/16" hole would be sufficient, but would like to wait for the mysterious bulletin as well.
    PS-I’m "assssuming" your midsection has the shallow wall like the one mumbles has in his pictures.

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