Sears 9.9 overheating problem

[joecit]

I have a sears 1996 9.9 that overheats.I recently changed the waterpump,propeller,thermostat,head and side exhaust gaskets,but it still overheats.It will run cool and fine if i remove the thermostat,but once i put it back in, the head and exhaust gets too hot to touch and starts to overheat.Does anybody have a idea what could be wrong,i dont want to be robbed by the local dealer.The water pumps nicely with the thermostat out,but when i replace it the water just dribbles out,and quickly gets hot.Please help!

 

[steelespike]

Re: Sears 9.9 overheating problem

Are you sure the thermostat is right side up?
Put the thermostat in water and see if it opens at the temp indicated for it.
It appears the water flows correctly without the thermostat so something is up with the thermostat or the housing or gaskets etc.

 

[joecit]

Re: Sears 9.9 overheating problem

The stat is in right,i just cant figure out what is causing this.It seem the thermostat is blocking the flow,i tested it and it opens correctly.

 

[steelespike]

Re: Sears 9.9 overheating problem

Is there a bypass that is supposed to let some water flow past the thermostat.Maybe it is plugged.If the water doesn't circulate the motor might over heat before thermostat is hot enough to open.

 

[joecit]

Re: Sears 9.9 overheating problem

What do you mean by bypass? The stat opens,but liitle water flows thru it then it stops completly.Then the motor gets hot,if i take it out the water flows nonstop,do you think it can be a impeller problem? I just replaced both the impeller and waterpump housing.

 

[steelespike]

Re: Sears 9.9 overheating problem

When the motor is off there is no water in the powerhead.I'm no expert but it would seem to me there must be some way for water to enter the powerhead as
it is warming up.Otherwise the thermostat has no water
on it to heat it up so it opens.And when it opens you might be puting water through some really hot areas.
Perhaps there are small holes in the thermostat that let
a small amount through.
I'm still puzzled why you have proper flow without the thermostat but problems with it in.I don't think it is the pump. I'm grasping at straws here.There is a slim chance If there is a leak in the tube from pump to powerhead that the resistance of the thermostat may be enough to reduce the flow.
You might check compression and take a close look at the plugs.Thinking maybe some sort of screwy head gasket problem.If the impeller disintagrated there could be pieces stuck somewhere.

 

[drewmitch44]

Re: Sears 9.9 overheating problem

i know what u mean about stat blocking the flow. I have a 96 15 HP and when i replaced my stat wnen i put it in it was like how is water going to come through that tube past the stat. But it does. I bought a new stat and it didnt work water would not come out just dribbles. i got a second one with the same part number from quicksilver and it was longer and skinnier at the spring area. You want a stat that is 105 degrees. the second one worked fine for me. what i cant understand is that these two were the same part number!!

 

[John B.]

Re: Sears 9.9 overheating problem

I have a sears 1996 9.9 that overheats.I recently changed the waterpump,propeller,thermostat,head and side exhaust gaskets,but it still overheats.It will run cool and fine if i remove the thermostat,but once i put it back in, the head and exhaust gets too hot to touch and starts to overheat.Does anybody have a idea what could be wrong,i dont want to be robbed by the local dealer.The water pumps nicely with the thermostat out,but when i replace it the water just dribbles out,and quickly gets hot.Please help!

 

[John B.]

Re: Sears 9.9 overheating problem

Any chance the discharge water port(s) may be clogged? I had that problem with and older Merc that I had to occasionally put a wire into the discharge port.

 

[John B.]

Re: Sears 9.9 overheating problem

Any chance the discharge water port(s) may be clogged? I had that problem with and older Merc that I had to occasionally put a wire into the discharge port.

 

[John B.]

Re: Sears 9.9 overheating problem

You may just want to run it without a thermostat. It will probably run fine most of the year.

 

[joecit]

Re: Sears 9.9 overheating problem

I"ll try another thermostat,where are the discharge ports?Thanks Joe