79' 9.9 overheating :(

[89beretta]

My 9.9 is overheating. I have changed the impeller, impeller housing, water tube grommet, thermostat. made sure all the lines where clear of debri. made sure I had enough water in the barrel made sure there wasnt any debri in the barrel to get sucked up onto the intake. after installing all of these things I put it in the tank to do a test run. well it ran fine for about 30 minutes then I lost the stream of water coming out of the lower pan and it started spitting water and steam. I shut if off. what else can I do? can I remove the thermostat and run without it? go and get a diffrent thermostat. any ideas would be nice. thanks

 

[oldcatamount]

Re: 79' 9.9 overheating

sounds like the thermostat to me. You can check it by putting it in a pan of water and heating it to about 140 and watch to see if it opens. Sometimes even a new one won't work. If it was pumping water, that would say the impeller is OK and the intake is clear. Did you run the motor in gear in the tank and possibly blow out some of the water?

 

[89beretta]

Re: 79' 9.9 overheating

motor was in gear. but not fast enough to really do more than just churn it up. do you know if it will harm the motor to run it without a thermostat?

 

[kbait]

Re: 79' 9.9 overheating

Run w/o thermostat and see if the indicator stream comes back and not steamy. First, be sure you have the barrel water ABOVE the bulge in the casing containing the impeller. Just submerging to water intake won't prime the pump. You can run it w/o the thermo, just like a car, but it won't run efficiently... unburned fuel and such from too cool..
If it still gets steamy/intermittent stream w/o stat, either blockage or pump not pumping well. I've heard you can hook up a drill to the drive shaft and spin to see if the pumps working. Good luck.

 

[89beretta]

Re: 79' 9.9 overheating

just so im clear. I can run my 9.9 normally out on the lake without a thermostat and it wont affect the performance of the motor ( ie loss of hp or anything like that) it will only hurt the fuel economy????

 

[kbait]

Re: 79' 9.9 overheating

It won't perform as designed, it won't burn fuel completely at the cooler running temp, and it'll leave more carbon and gunk in your engine, and carbon buildup can kill those motors.
It will function adequately, but I have mine in there. I also do a decarb annually on mine, just to be sure..

 

[dazk14]

Re: 79' 9.9 overheating

1st off...

You may not have a problem, running it for 30 minutes in a tank can easily heat your cooling water through the roof and the motor will overheat.

Is this a long shaft motor - there is a part that is often missing in the L/u that is needed for best cooling.

Did you replace the upper water pump housing seal that seals to the drive shaft?

Was the steam coming from the exhaust relief ports on the back of the motor or from the tell tail?