1999 Mercury 150 intermittent water flow

[yankee]

I started the motor on the ear muffs in the driveway before an outing and water was streaming from the weep hole as usual.  Left the dock at the lake and water still streaming from the weep hole as usual.  Tooling around on the lake and looked at the motor, and nothing bust steam being forced from the weep hole.  Stopped the engine and sat on the lake for approximately 30 minutes, fired the engine up and water streaming from the weep hole as usual.  Headed for the boat ramp and after about 5 minutes, nothing but steam blowing from the weep hole.  Stopped the engine again and waited a few minutes and started the engine back up and water streaming from the weep hole again as usual.  Made it to the dock blowing steam again.  I have no idea where to begin?  It appears that the impeller is pumping water and the impeller was replaced last year.  Could the thermostats be sticking?  Could there be some dirt in the water chambers that cannot get washed out?  Any ideas as to where to start?

Thanks Guys

[Juan]

Could be one of several things. Did it run hot when it stopped peeing? Did you get an overheat alarm? You might try putting your hand on the engine block when it stops peeing to see if it's hot. If it's cooling properly, you should be able to hold your hand on the block. Have you had the same problem since the impeller / water pump was changed? (I ask because it's possible the impeller vanes were installed in the wrong direction.)
My first guess would be a blockage in the hose running to the pee connection. (Maybe a mud dauber nest or seaweed) Try running a weed eater string or piece of 100 or 150lb mono up the weep hole as far as you can. Try disconnecting the tube at the weep connection and engine block and try to blow through it.
My second guess would be a thermostat is stuck closed. You could either remove or replace the thermostat but you can also check them by using a lighter and applying heat to the bottom of the thermostat. It will open if it's working properly. A safer way to check to see it they are opening is to place them in boiling water.
Lastly, the impeller might be damaged.

[yankee]

Since the new impeller was installed, it has run like a champ. No problems at all. When I stopped the engine I took the cowling off and it was hotter than Africa. Some of the wiring wrap was melted to the valve covers, but it peeled off easily with no visible signs of damage to the wiring. It is almost like something might be "floating" in the water jackets or circulating lines. When I start it back up after sitting, it will go about 5 minutes before the tell tale stops spraying water. While water is coming from the weep hole it is a strong stream and appears to be doing as it always has? Then water stream stops and steam starts coming out and you can hear it hissing through the weep hole. I have ordered a new pump kit and thermostats.

[Juan]

It does sound like something moving around in the cooling passages. You might try removing the thermostats, connecting the muffs and try to flush it out through the thermostat holes. If nothing flushes out, I'd leave the thermostats out and run it to see if it runs hot. If it does, you'll know it's the water pump, if it doesn't, install new thermostats.

[yankee]

How does the flush port where you connect a garden hose function? Could that flush anything out of the system?

[Juan]

I believe the flush ports flush a portion of the engine block. That might work if you're lucky but a blockage won't get past the thermostats. Starting the motor briefly with the muffs connected and the thermostats out will throw a lot of water out the thermostat holes if the water pump is pumping as it should and it should force any blockage in the entire cooling system (not just the block) out.

[yankee]

I just ran some water through the flush port and both thermostat housings have a small drip coming from them. Going to remove the thermostats and see if I can wash anything out through the t-stat outlet in the cover.

[yankee]

T-stats look pretty cruddy.

[yankee]

ran water through the flush port with the t-stat housings off the covers. Nice clean water coming out, plugged one side with my thumb and more pressure to the other side. I did not fire the engine up with the t-stat housings removed. Put everything back together with out the t-stats, started the engine and no water coming out the tell-tale. Ran until the valve covers warmed up fairly good, about 3-4 minutes, still no water from the pee port so I shut her down. I'm guessing the impeller is gone. New one will be here sometime Monday along with the thermostats. Fingers crossed.

Thanks Juan for chiming in, greatly appreciated.

[yankee]

I have the two new thermostats installed and engine runs and circulates water pretty much normal, might appear a bit weaker than normal, but not sure.

A new impeller kit is going in when I receive it.

So now, how do I prevent this. I have no warning buzzers, warning light, or a temp. guage nor a pressure guage. I am thinking at the very least I need a temp guage installed? I have a sensor in each head, but not sure what I have under the helm as far as wires. I am thinking that there are wires there from the sensors, but which ones? I can follow a tan/blue and a tan into the bullet type connector inside the engine space. Where they go from there I do not know.

[yankee]

Edit: Only 1 sensor

Attachments:

[yankee]

Also, previous owner removed the oil injection system. This may be why there are no warning buzzers.

[gnrphil]

Oct 4, 2021 12:52:18 GMT -6 yankee said:

Also, previous owner removed the oil injection system. This may be why there are no warning buzzers.

More than likely. The wiring for the temp alarm should be in the engine wiring harness in the console, are there no warning lights on the tachometer?.

[yankee]

Not any type of warning indicators are present. While out on the lake, if I would not have looked back at the motor I probably would have done major damage.

[Juan]

According to the wiring diagram, the tan or tan with blue stripe goes from the engine's sensor to either a horn or temp gauge. Are they connected under the console?

[yankee]

Ok, as for the wires. The tan/blue striped wire comes from the sensor to a terminal block mounted on the crankcase, continues through the cable going to the helm. Comes out under the helm and connects to one wire going to a piezo buzzer, then joins a 2nd wire going to a 5 pin connector which is not connected anywhere and has no mating connector that's visible. The buzzer has a 2nd purple wire which goes to the ignition switch. Can I eliminate the piezo buzzer and replace with a temp guage?

[Juan]

You can certainly eliminate the buzzer and install a temp gauge in it's place and use existing wiring but I'm pretty sure the heat sensor and the gauge have to be a match so you'd have to change the existing sensor.

[yankee]

I am looking for the sensor on-line now. Also, the existing sensor has a good amount of corrosion around the mounting strap and between the strap and the valve cover. Do I need a sensor for each cover, or is one enough to get a correct reading on both sides of the engine?

[gnrphil]

You'll need one on both sides.

[Juan]

Oct 5, 2021 9:50:29 GMT -6 gnrphil said:

You'll need one on both sides.

Here's the part numbers for both port and starboard sensors in case you haven't found it yet: www.crowleymarine.com/mercury-outboard/parts/3998_150.cfm?mdl=RBSQSU
(numbers 10 and 17)