Installing a telltale

[amuller]

I’ve been wondering if that blank port on some thermostat covers was intended for a telltale.

This is the most sensible write-up on this I’ve seen:
http://forums.iboats.com/forum/engine-r … -tell-tale

The idea here is to put the pee-hole source directly into the upper water jacket. Definitely agree that the pee-stream should be put where readily seen.

[fleetwin]

True, the way the pictured telltale is set up might just be bypassing the thermostat….Would be hard to tell without removing the cap and checking out how the water is supposed to flow….Needless to say, the engine won’t come up to temperature if the pictured set up is problematic.

[dan-in-tn]

Well let me see how many holes I can shoot into the article written by Iboats. No ill will towards them, but they got caught up in a motor design change & either didn’t notice it or didn’t know it was important. The bulletin they show is for 1986 (CD) 1987 (CU) & 1989 (CE) motors. These are 56 cu in motors that don’t even have a powerhead (49 cu in) like shown in the picture. It is true the 60hp motor continued to be made as a 49cu in motor till 1989, but did not suffer from the problems early 56 cu in motors did. (The reason for the bulletin in the first place). Putting the over board telltale in the top of the block would definitely add to over cooling. At least they do recommend the factory fitting in the pan. That fitting has a small hole which keeps a small amount of water from being expelled. Since they have a tendency to become clogged people do away with them and just stick the hose out of the pan. This is unacceptable. Remember the more water you let escape here, the more cold water you let into the system to over cool the motor. The thermostat no longer controls that.
Now the 56 cu in motor tells/shows you to put the elbow at the top of the exhaust area of the block. That can’t be done on the 49 cu in motor because of differences in design. The exhaust cover on the 56 cu in motor is actually just a water cover. If you take it off you don’t see inside the motor, only the water jackets. Because they got the models crossed or confused it hurt the article a lot in my opinion. Of course this is just one model, but there is enough confusion on this model engine already.
The main thing to take away from this is you have to think about the whole system before drilling & changing things to make improvements. Our aim is to make our engines more environmentally friendly while we protect them from costly repairs.

Dan in TN

[pappy]

Another option for the remote operation set-ups would be a simple water pressure gauge.
It will always tell you if you are good to go since you develop a running knowledge of what pressure to expect at a given throttle setting.
With one on the dash there is no longer a constant need to turn around and look.

1 user thanked author for this post.

amuller

[amuller]

All true. Any liquid cooling system needs to be able to deal with air and other "non-condensible" gases, or at some point it is likely to get air locked and overheating will result. this means in practice that some means of venting from the highest point of the system is needed. Many cars do not comply with this because styling and aerodynamics results in radiators lower than the highest point of the cooling system. This often works when new but gives trouble as things age and leak. I’m learning that outboards have similar problems. There are various reasons why the water pump is likely to pump a certain amount of air and if this exceeds the ability of the system to get rid of that air bad things will happen. So I like the idea of a telltale at the highest point. Obviously this should not flow enough to defeat proper temperature regulation.

Chrysler has used pressure gauges, but I don’t think this is a complete solution as the gauge can’t distinguish between air pressure and water pressure.

[amuller]

It´s interesting to go back to this thread after an actual overheating experience.

Am very glad to have the telltale. While imperfect it gives a strong degree of confidence that water is pumping.

Where I put it, near the back of the pan pointing down, is not really convenient for monitoring from the steering position. It needs to shoot sideways or up like a jetski. An easy fix.

I looked up water pressure gauges and they seem to be 0 to15 psi or 0 to 30 psi. https://www.iboats.com/shop/searchrabbit/result/?q=water+pressure+gauge Will put a gauge on the telltale line and see what readings I get.

[fleetwin]

Like Dan says, we have to be careful adding telltales, and consider the effects they will have on proper cooling system operation. That all begins with a good understanding of the cooling water flow through the particular engine you are working on. I am really tired of all the “online experts” going on about systems they don’t really know everything about. The conventional OMC method of tapping into the exhaust manifold is far from perfect, but tapping farther down the cooling system can show a telltale flow that is inconsistent, or hot, which is going to create problems with thinking there is a problem, when there isn’t one.
In Amuller’s case, I think Pappy’s advice about a dash mounted water pressure gage makes the most sense, except that I don’t think he has his telltale tapped into the exhaust manifold. So, it is hard to know what pressure readings are to be considered normal…..
And, unfortunately, many cooling issues occur instantaneously and at higher RPMs, so chances aren’t good that you will be looking at a telltale or gage when the issue occurs. You only look at the telltale or gage once the engine overheats and falters, which is usually too late.

• This reply was modified 3 years, 6 months ago by fleetwin.

1 user thanked author for this post.

amuller

[rudderless]

Several years ago I had spent all winter going over my 76 15hp for my jon. Put the boat in the water in spring and went about 1 mile and turned around. Motor sounded off song so I turned it off. Tilted up the motor and a plastic bag fell off the lower….overheated a little. Took it out the water and installed a pisser outlet a foot in front of where I sit so I can see it on the side of the boat. If ya are going through the effort to install a pisser put it where ya can see it.

1 user thanked author for this post.

amuller

[amuller]

One obvious issue here is to keep the telltale volume as low as possible, low enough so as not to seriously disturb the cooling water flows. At the same time, we don’t want an orifice so small it will routinely clog. Anybody have numbers?

How do we understand OMC producing motors without thermostats, such as the “33” hp skitwins, etc.? It seems these would be over-cooled most of the time…..

[amuller]

After a bunch of reading on this I’m installing a 1 to 30 psi pressure gauge, connected to the pisser connection. Using a gauge I had lying around, and some 1/8″ drip irrigation tubing. (This is essentially the same stuff used to hook up pitot-tube speedometers.) We shall see how it goes, but it seems that a gauge might give advance warning of pump impeller deterioration…..

[Author]

Posts