QD19 running a little hot?

[beerman57]

I would love for it to be as simple as a clogged hole between the 2 cavaties in the mid. I hooked up the garden hose to the water tube, listened to the exhaust housing with a screwdriver and could hear water running. I’ll take a good look at the ’62’ mid tomorrow.

[jeff-register]

Robert,
In the manual it states water flow to the relief holes becomes too much to drain filling the relief holes. This forces the excess water to travel to the main exhaust cavity to cool your exhaust gasses & shift handle. I tried to send you a e mail with a manual photo but my e mail program is screwed up now & need help, With your 58 together get a very slow hose flow & try to fill the relief cavity. If the passage way to the main area is plugged the water will not drain into the exhaust cavity. That will tell you in a heart beat if it is clogged.
Jeff

[fleetwin]

Jeff has a good point. You could also try starting the 58 on the boat in the water cold and noting whether or not any exhaust escapes from the cooling outlet during start up. If not, perhaps the relief is plugged. Fogging the engine prior to shut down might make it easier to monitor exhaust relief from the cooling telltale during cold start up.

[beerman57]

So exhaust should be coming out the telltail because of the relief holes. I’ll look on the ’62’ first to try and find the relief holes, then pull the QD19 P/H again – at least it’s pretty easy to remove and has not been run since being re-installed. I wonder, hhmmm, might doing what Jeff said – plugging up the telltail hole and hooking up the hose to the water tube, if a little water pressure might open up the relief holes?

[jeff-register]

Robert,
You can’t plug up the holes. Just get the hose flow enough to keep the cavity full of water. If the hose overflows your passage way from the relief holes going into the leg should allow water flow to go into the main leg to coolthe main exhaust. Lay your motor flat on the clamps so the relief holes are flat also. The extra water should go into the main part of the leg for cooling. I believe that is the problem. All the water flow now is exiting thru the relief holes & none is going into the main part of the leg. This too slows cooling for the powerhead as the exit passage way is restricted as well. Did you get my e mail? If not I’ll try again from another computer here.
Robert, I’m excited today. I recieved my 1953 Firestone 10hp motor. The bearings in the lower unit are trashed but I have new ones.

[beerman57]

Jeff, I didn’t get your email. Send some pics of your new motor if you can.
OK, the relief hole is more like an overflow hole. It comes out inside the exhaust cavity at the rear of the mid, about the same level as the telltail. I don’t see how that will cool the exhaust, not much water will ever find it unless the telltail cavity is full of water, plus it comes out about 7.5" above the mating surface of the lower unit and mid, that’s pretty far down. I don’t even think it’s clogged up on the QD, I shined a flashlight up the telltail and saw a little bit of light looking up the mid.
What is the purpose of the cover a couple inches down the rear section of the exhaust cavity? 2 bolts hold it in place. #2 on this diagram.

http://www.marineengine.com/parts/johns … Lower+Unit

[jeff-register]

Robert,
I need to dig in the service manual to see about the plate. We spent 3 hours fixing my computer & I resent the scan from the service manual. Please let me know if you recieved it. If not I have more computer work! Stick a pipe cleaner up the pipe to see how dirty it is too. Do you have the plate installed? Looks like a block off plate.
Jeff

[beerman57]

I got lazy today and didn’t hook up the garden hose to the water tube on the QD. That would prove if the relief hole is clogged or not. I thought maybe with that plate off, it would help with the mid overheat problem, that plate doesn’t seem REAL important to me, but without it maybe the exhaust could leave the mid easier and help with the heat problem. AND maybe give a little boost in HP? The easier exhaust can get out, the better?

[jeff-register]

Robert,
That plate must be there for some reason or Johnson would not pay to have it made. Two strokes require a tuned exhaust to function. I would research it further before leaving it off. I’ll do some looking in the manual tonight to see what it is for. It may cause more water to exit & cool somehow.Anyone else know?

[beerman57]

Well, it’s not the relief hole in the water discharge. The only thing I can think of to do now is to run it with the cowl off and see if the cyl. head is hot after being up on plane. I’ll say it again, it runs great, plugs are dark. The shift handle cools down after being up on plane, but not the mid. The impeller, wear plate & housing are in good shape. If the P/H doesn’t run hot on the boat then I don’t know – it doesn’t run hot on a hose in the driveway.
I could always waste 40 gallons or so of water and run it in a barrel, but I don’t think that’s a very good test.

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