Mercury 150 to Corm

[savage]

My 150 merc has a extremely hot tell-tale stream, the water actually has steam vapors coming off of it. Is this normal? I can't ever remember seeing one this hot. I don't know what the water pressure is because the gauge is broke, but I have one on order. Should I be checking anything else? I ran the boat in a bass tournament today and covered some 30 miles and the temperature horn never went off, but the tell-tale was almost scalding hot everytime I checked it. Can anyone offer any words of wisdom?

 

[holbor]

Re: Mercury 150 to Corm

I had a similar question to yours. I have a 200 hp. 1988 Merc. I did a little testing and found my tell-tale water temp. was about 165 F (it is also too hot to touch for any more than a second) and my head temperature was about 180-190 under the top spark plug. I am still not sure exactly if my motor is running a little hot or not but here is some insight. Most outboard motors have the tell-tale coming out of the block before the water is used for cooling. In the case of my motor (and I believe yours as well) the tell tale comes out of the thermostat housings after it has cooled the engine. This is why the water is a lot hotter than most and also why the tell-tale stream may be weak until the motor has warmed up (when the thermostats begin to open fully) Hope this helps and I am interested to see any other replies you get, Mike

 

[savage]

Re: Mercury 150 to Corm

Just to be on the safe side I replaced the impeller today, it was three years old. The old one didn't look that bad, but it had started to take a set. Tested the thermostats on the stove,they opened at the correct temperature (143) I'm waiting for the pressure gauge to come in before I lake test it again, probably Wednesday. I did learn that the water on the stove was smoking at 143, maybe I'm chasing a ghost!

 

[corm]

Re: Mercury 150 to Corm

Hi Savage,<br />Holbor is on the right page, the teltales are hot water. The motors will run hotter than the thermostat by 10-25 degrees with no problem. One thing I run in to is that the poppet valve spring is weak and doesn't let the block fill up all the way at low speed.<br />This causes the motor to run hotter than normal, but it should cool down at speed.<br />It is located on the starboard side of your block at the bottom of the block, held in by 4 small bolts. There is a rubber diaphram in there also that can't be tore or have holes in it. You probably are chasing ghosts, but it was a smart idea to replace the impeller<br />and check the thermostats. The pressure gauge<br />is what I like the best, glad you have one.<br /><br />...have fun...corm

 

[savage]

Re: Mercury 150 to Corm

I did check the poppet valve for debri and found nothing, it seemed to be seating ok. I'm still waiting for the pressure gauge to arrive so I can lake test it. Thanks for the reply Corm.

 

[Salmonator]

Re: Mercury 150 to Corm

I just bought a trophy with a 150 blackmax (I believe it is a 1995) and noticed today that the water out of the indicator is also too hot to touch for more than two or three seconds. At cold startup it just spits and sputters, then as it warms a nice stream and then a fast stream at cruise. I would also appreciate any more comments on this as I will be running up to 18 miles offshore every few weeks and don't want to have the coasties towing me in... Joe