June 23, 2015 at 2:30 pm #18766
Hey Beer, I found several different year mid sections late yesterday and they all had minor differences in them. When I get back in a few hours, I’ll take some pics and also run up a few motors, including a ’58 QD. 😀June 23, 2015 at 3:07 pm #18768
OK, I am assuming you had the powerhead on when you plugged the overboard cooling dump, then saw water leaking out of the triangular hole I mentioned. So, if that is the case, I think it is safe to "assume" that the exhaust relief/cooling circuit buried inside that cavity is working as designed. It can’t hurt to pull that plate off and have a look, but only if the screws will come out with no torching involved. Definitely reinstall the SS plate though, don’t leave it off.
I would hesitate to drill the cooling relief holes in that cavity above the SS plate though, that is pretty darn close to the exhaust manifold. Negative exhaust pressures could actually draw water up into the exhaust ports, crazier things have happened!
Hold off on drilling holes into the #2 cylinder water jacket until someone can confirm this is accepted practice with a bulletin or by actually finding a block with a relief hole in that area.
I think Mumbles will be able to provide some good data when he runs several of his QDs looking for a hot midsection/shift handle.June 23, 2015 at 4:14 pm #18773
fleetwin, at this point I’m not going to get in a big hurry to drill any holes. But where about are you saying I might drill into the #2 water Jacket? After looking at the P/H base and top of the mid, I don’t see any likely places to drill a hole. I can send pics of my P/H and mid, but don’t seem able to post them here from my computer.
If I ever get the right base gasket for the ’62’ ten hp. I can play with that one. But with my luck, it will have the same problem.
Topics: 32June 23, 2015 at 5:48 pm #18776
I’m seeing mention of both "tell tale" and "exhaust relief":
To me, a "tell tale" is water tapped from the cooling system and "peed" out to indicate that cooling water is being pumped…. OMCs of this era don’t have those (unless you’ve tapped the cooling system yourself)
To me, "exhaust relief" is the hole on the back of the leg where exhaust and water come out…June 23, 2015 at 10:03 pm #18780
Today I pulled out both a ’58 QD carcass and a running ’58 QD to see what’s going on. Just like I expected, not much.
The ’58 midsection is designed a bit differently than the earlier ones. The web in the middle separating the two chambres is only 5/8" or so deep while the earlier ones are closer to 5" deep. This allows the hot gases to immediately flow into the shifter area after leaving the cylinder. Some of the exhaust gases travel to the bottom of the housing before coming back up the rear chambre thru a small triangular hole near the bottom. The plate at the top seals off this part of the housing forcing the gases to discharge thru a hole about the size of a nickel into the rear water exit passage and out thru the idle relief port.
After running the motor at both idle and top barrel speed for several minutes, the housing temperature in the shifter area never changed more than ten or fifteen degrees. The shift handle itself never got much more than ninety F which was about the same for everything else in the direct sun today. In other words, the housing and the shift handle were both at good operating temperatures and I wouldn’t have been able to boil water or fry eggs on either of them.June 23, 2015 at 11:48 pm #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.
Canada Member - 1 Year
Topics: 157June 23, 2015 at 11:56 pm #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.June 24, 2015 at 1:25 am #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.
Canada Member - 1 Year
Topics: 157June 24, 2015 at 1:38 am #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.June 24, 2015 at 5:05 am #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.June 24, 2015 at 5:18 am #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.
US Member - 1 Year
Topics: 41June 24, 2015 at 2:00 pm #18814
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.
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.
JeffJune 24, 2015 at 3:34 pm #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.June 24, 2015 at 4:08 pm #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.June 24, 2015 at 4:12 pm #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.
You must be logged in to reply to this topic.