Water temperature or head temperature

[Daniel1947]

I have a 1989 Mercury V6 150 HP Black Max. Is the temperature gauge actually a "head" temperature gauge instead of a "water" temperature gauge. While considering replacing the temperature gauge, I realized that the sender is in the head and not actually in contact with water flowing through the engine. I had thought about installing a "T" block in the tell tale with an actual temperature sending unit which would give me a temperature reading of the water leaving the engine. Anyone have any ideas about this? Thanks to all. Dan

 

[Faztbullet]

It is a head temp gauge and does not measure water temp, that why gauge just has range of cold thru hot and not sectioned off in degrees. You better off with a water pressure gauge than a temp gauge as reading is instant..

 

[Daniel1947]

Thanks....But where would a "pressure" gauge be installed. And because I am looking for information, why would a "pressure" gauge be better than a "temperature" gauge on an outboard.

 

[Faztbullet]

Pressure guage would attach into top of block. A wp gauge is better as you can monitor the condition of impeller as it wears,can watch the t-stats and poppet open at different rpms, if you run over some debris and shut off water flow you will see pressure drop to zero way before a warning horn sounds and if you have a jackplate it helps in fine turning your setup for max speed and performance.

 

[Daniel1947]

Makes sense as long as there isn't a chance for overheating of the motor. I understand that unlike a closed system on a vehicle, there is a constant flow of fresh cooler water running into the motor. I was thinking more about a possible overheating condition, but now I see that is possibly almost not a problem as long as the water is flowing through the motor. I have been looking at my Mercury owners manual, and have also removed the cover and looked at the motor. Can you give me some idea of where "you" would install the sender as you said, "into the top of block." Thanks again for your expert advice.

 

[Faztbullet]

It would go in block at #19 on diagram......

 

[Silvertip]

And I contend that both temperature and pressure gauges are preferred (at least in my view). Although it is getting tougher to find outboard temp gauges that have a 60 degree starting point, they are typically 100 degrees but then that's still better than nothing. As pointed out, many are just "C" (cold), "N" (normal) and "H" (hot) but none of those tell you what the actual temperature is. Water pressure indicates there is pressure in the system. It is not an indication that all is well temperature-wise. Only a temperature gauge can tell you that. If I had my choice of one or the other it would be water temperature. I can turn my head to see if the tell-tale stream is present or not. I usually do that the same time I glance to the rear to see who is about to run over me.

 

[Daniel1947]

I appreciate the information as always. My idea of an actual water temperature gauge installed into a "T" block in the tell-tale would give me an indication of the actual water temperature leaving the motor. It would not be difficult at all to install it there. We used to use "T" blocks in our fuel lines on our drag cars to indicate fuel pump pressure. I think I am going to install both since a sudden loss in water flow may not be immediately noticed, nor a possible temperature increase. Either way, $75 to $100 for a couple gauges and install kits sure beats a motor. Thanks again.

 

[Daniel1947]

Got the cover off the motor and found the fitting referenced at #19. There is a hose that runs from the existing fitting down to another fitting on the side of the block; I am sure this is just to assist with the water flow through the motor. My plan now would be to just "T" into this hose for the pressure gauge line. Anyone see a problem doing that?