Tell-tail location

[Chris]

I have a 1972 Evinrude 50 horsepower. I am about to install a Telltale or what some would call a pee hole.

All the information I have found out there shows that you would drill into the water jacket forward of the head gasket. I understand that this location will only show if the impeller is working. But it does not show if the thermostat has opened. Has anybody ever installed maybe a second pee hole on the backside of the thermostat, as in the head area instead of the cylinder area?

[fleetwin]

Well, usually the telltale elbow is located in the exhaust manifold cooling jacket, which is the beginning of the cooling circuit in the powerhead. The problem here is that the original exhaust cover on your 72 50hp does not have a threaded hole for the elbow, or a boss on the cover suitable for drilling. You certainly could drill through the water jacket on top of the block, forward of the head gasket and install an elbow there. The problem is that you must be very careful drilling to avoid drilling through something you don’t intend to drill through.
No matter where you place the elbow, good water flow from the telltale does not guarantee the engine is cooling correctly. The three cylinder models have an elbow drilled through the top of the block in the exhaust cover/manifold cooling area, this helps ensure no air is trapped there.
Again, I want to emphasize you must be very careful where you drill, or you might make a terrible error. I guess the easiest way to figure out where you can drill safely is to have a donor/dead/damaged powerhead that you can pull the exhaust covers and head off. You can do test drillings on this piece instead of possibly damaging your powerhead.
Trying to drill through the cylinder head water cover in an attempt to put the telltale "after the thermostat" would be near impossible. The cover is very thin, and the passage in the head is very shallow.
No matter where you put the telltale, it is unlikely you will be watching it if the engine overheats suddenly at high speeds…I "think" your 72 50hp uses a hot horn, check this feature and make sure it is working properly. Simply turn the key on, separate the knife connector for the temp sender, then ground the powerhead end of the tan lead to the block, the horn should sound…..

[frankr]

There is always water "downstream" of the thermostat (because of bypasses). This is necessary in order to provide cooling for the exhaust. So attempting to discern if it is open or closed would be futile.

[Chris]

Thank you for the replies. Excellent points.

I founds these pics….

I sure don’t want to be a "pioneer" on drilling the motor, but looks like there’s precedence for this location.

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[fleetwin]

OK, my reply didn’t post…So, once again…
I don’t think you can get in much trouble locating the telltale elbow as pictured here…However, I would probably use the standard OMC plastic telltale elbow to avoid possible corrosive effects of dis-similar metals…
I would not attempt to drill through the top of the exhaust manifold (under the ID core plug) without having a donor block to "practice on"…D

[Chris]

Yep, just picked up the OMC plastic elbow and fitting for cowel. It takes a 1/8 pipe thread tap. Hardware store did not have one, but auto parts store did.

[donsmarine]

some Mercury outboards had telltale at thermostat,only would show stream when it opened.

[need2fish]

Be very careful not to place stress on the elbow or the exit tube during motor operation.

The intent of a boss is to thicken the metal to make for a more robust attachment point. Drilling straight into the water jacket may mean an eventual crack in it.

[Chris]

quote need2fish:

Be very careful not to place stress on the elbow or the exit tube during motor operation.

The intent of a boss is to thicken the metal to make for a more robust attachment point. Drilling straight into the water jacket may mean an eventual crack in it.

Great point. Yes, the jacket is thin there. I feel better that the elbow is plastic, and also protected by the lifting eye. I had to mount the eye facing the other way (not shown in the photos above), but it protects the elbow a bit having it on there.

[Mumbles]

Apparently, OMC had sent a bulletin out instructing their techs to relocate the telltale fitting to the top of the blocks from the side of the exhaust area as the side location would still allow water to squirt out of the telltale even if the water jacket was half full from a weak pump. Moving it to the top of the block also bled any air out of the system ensuring the top cylinder was being cooled.

I learned the hard way (as in expensive) how important this was years ago on a 70 horse Johnson and now I move them on any two or three cylinder motor I work on with the old side location takeoff for the telltale. Removing the cylinder head makes it easier to see just where to drill for the fitting as the water passage can be tight around the cylinder. Tapping just enough thread to hold the fitting will prevent it from bottoming out on the cylinder, which will cut off the water flow to the telltale.

The lifting eye only mounts one way with the flywheel on so clearance for it has to be taken into consideration to.

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