Suzuki DT9.9 cooling/exhaust problem

bassmanisme

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Jul 1, 2008
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At idle, water sometimes stops pumping. Insalled new impeller kit, same problem. When running on the lake no problem - plenty of cooling. I noticed at idle and not moving the exhaust is not comming out of the back of the prop like it used to, most is comming out just in front of the prop. Ran the motor in a clear bin today so I could get a good look and sure enough the exhaust bubbles are coming out in front of the prop go straight up and get sucked into the water pump intake under the cavitation plate. Pulled the prop tonight and can see no problem. There is no seal (not supposed to be) between the lower unit and the prop, the prop is not damaged and the rest of the lower unit is tight, no oil leaks. I've had this motor for 15 years and never had this problem before.
 

deejaycee_2000

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Mar 28, 2006
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3,447
Re: Suzuki DT9.9 cooling/exhaust problem

seems like your prop is not sitting right back in it's place, take the prop off and see if all is still good .....
 

bassmanisme

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Jul 1, 2008
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Re: Suzuki DT9.9 cooling/exhaust problem

Thanks for the repsonse. The prop is in the right position. There are no issues there.

Further reading on the internet has convinced me that there should be no exhaust coming out the prop at idle, it should be coming out the idle relief hole on the back of the motor along with some water spray. The backpressure of water from the lake should prevent the exhaust from coming out the prop at idle.

This leads me to believe I have an exhaust clog somewhere between the block and the idle relief port on the back of the motor leg.

Anyone agree or disagree? Or can you confirm no exhaust should come out the prop at idle when running in water?

Thanks!
 

James R

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Feb 1, 2007
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2,660
Re: Suzuki DT9.9 cooling/exhaust problem

When you replaced the impeller did you notice any bad scoring of the plate or the cup. This will reduce dramatically the water flow from the pump. Dont ignore this issue or you will have an overheat at idle.
If there is scoring you must replace the defective items.
 

bassmanisme

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Jul 1, 2008
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Re: Suzuki DT9.9 cooling/exhaust problem

Just to close the loop on this one, I fixed my motor. Turns out my idle speed was way to high and forcing exhaust out the prop at "idle". Normally at the proper idle speed all the exhaust comes out above the water line - no bubbles beneath the water. My idle was set too high because it would not idle at the proper low speed. Took apart the carb and soaked and cleaned all the jets and passages, replaced the pump diaphrams while I was there, checked the float height, reassembled the carb, and all is good. By the way, don't put the carb to engine gasket in upside down the fuel pump will not work because the vacuum port is blocked by the gasket. Learned the hard way - duh.
 
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