1989 Force 125 hp Over heat alarm when put in gear

[fishbait2]

I have a 1989 Force 125 hp outboard. Just started to have an issues with the over heat alarm coming on after running for a few minutes in Neutral and shifting into gear. When in neutral and running it pumps water great and is fine. But when shifted into gear the Over heat alarm comes on. Beginning of the season a new impeller was put in. There is a very small tell tail installed on top of the thermostat area and sprays only a pin hole of water. The exhaust area sprays a lot of water. Motor runs fine. But I did notice the tell tail stops water spraying when put in gear then if I push up the throttle while in gear it starts again. All the while water continues to spray out with the exhaust area two holes behind the motor. RPMs in Neutral are around 800. The boat has been out about 7 times this year and not run more then a mile or so at a time a drift fished.
starting and running many times. I ran the motor in a 100 gallon tub at home and it ran the same way , perfect in neutral but the alarm would go off a few minutes after shifting into gear. Any suggestion are welcome. I did use a Lazer temp gauge and end checked the thermostat area and it showed 134.

 

[jerryjerry05]

Test the sensor.

 

[Jiggz]

With slow spray on the tell tale by the t-stat, it could be the t-stat is blocked or not working anymore. Try removing the t-stat and test if the alarm goes off again (without t-stat). Then test the sensor itself, as mentioned. If sensor tested ok, it could be the key on the impeller was not properly installed or maybe not installed at all.

 

[The Force power]

With slow spray on the tell tale by the t-stat, it could be the t-stat is blocked or not working anymore. Try removing the t-stat and test if the alarm goes off again (without t-stat).

The tell-tail is before the thermostat, isn't not?

 

[Jiggz]

The tell-tail is before the thermostat, isn't not?

It's on the t-stat cover but not really sure if it is before or after the t-stat. But a slow flow on the tell tale is an indication that not enough cooling water goes to the cylinder water jackets, if the tell tale is before the t-stat. But if it's after, it means the t-stat is either not opening or just like before not enough cooling water going into the cylinder. So by testing with the t-stat remove will yield a good diagnose of the problem.

 

[fishbait2]

It's on the t-stat cover but not really sure if it is before or after the t-stat. But a slow flow on the tell tale is an indication that not enough cooling water goes to the cylinder water jackets, if the tell tale is before the t-stat. But if it's after, it means the t-stat is either not opening or just like before not enough cooling water going into the cylinder. So by testing with the t-stat remove will yield a good diagnose of the problem.

Tell tail is after and above the T-stat, it is a 110F stat. I ran the motor in Neutral and tell tail sprays water and water comes out with the exhaust from the two holes behind and just below the power head as its suppose to. I shift into gear and the waters stops coming out of the tell tail above the T-stat. I slightly rev and water comes out again but the alarm starts going off. I have been told to drop the gear case and check the water supply to T-stat.Than do a pressure check of the gearcase, replace any bad seal. And replace the impeller and seals under the gearcase gear oil cap.
To start I am replacing the T-stat and go from there.

 

[Jiggz]

"I shift into gear and the waters stops coming out of the tell tail above the T-stat."

The water spray from the tell tale stops is because a load on the drive shaft slows it down a little but THAT IS TOTALLY NORMAL. Now what a little slow in drive shaft rpm could that have affect on the impeller, UNLESS THE IMPELLER IS JUST SLIPPING OFF THE DRIVE SHAFT, MEANING IT'S NOT KEYED. And it only turns because of water or hydro coupling or fluid coupling between shaft and impeller inner slot. Your next step should be to drop off the LU and inspect the impeller first. Removing the t-stat may not even be necessary. But if after inspecting the impeller and the problem continues then next should be to remove the t-stat just for more troubleshooting. You can also check for blockage while the LU is out. Insert a garden hose to the water tube and slowly open the water spigot and see water gushing out of the exhaust snout.