9.9 2 stroke ‘91 cooling issue

[DIY1111]

)&£¥>^* !!!

Feel better already.

Engine starts and runs perfect.

Water flows out of telltale at idle, while in a large barrel. When put into gear, and brought to a higher RPM, the telltale stops flowing. When put back into neutral and idle, the tell tale will not return to function.

Replaced impeller and rubber grommet for water intake at the water pump.

Removed LU, and ran vinegar through intake while clogging telltale. Also, ran diluted muriatic acid in the same way. Reversed acidity with baking soda and water. A lot of scale was removed.

The only thing I can think of that makes sense, is that when in gear and propeller churning water the LU water intake sucks air and for some reason is unable to re-prime once back underwater. If I remove tell tale hose from exhaust plate, and reverse water boa garden hose, while engine gets running - this will ‘re-prime’ water flow.

Telltale runs indefinitely at idle…

An open water test would help test this theory.

Am I missing anything? I know there is a possibility that the cooling system in the engine and heads could be clogged. But, all ‘seems’ to flow well when LU removed, garden hose connected to intake tube.

Opinions welcome as I have spent more time on this then I wish I had.
An open water test would help test this theory. Am I missing anything? I know there is a possibility that the cooling system in the engine and heads could be clogged…

 

[Sea Rider]

That's a 20 year oldie motor, if salt water used expect to be full of internal salt, crap, whatever was formed inside the water passages. Run compressed air as you did with plain water through the lower pick up tube..

Happy Boating​

 

[DIY1111]

Did the air. If the vinegar and then acid didn’t do it, the engine would need to come off and would need to be disassembled to be cleaned. (1) bolt on exhaust and (2) bolts lower on the cylinder heads feel like they’ll be b*tchy to remove, with a high snap! probability.

 

[Sea Rider]

Did the air. If the vinegar and then acid didn’t do it, the engine would need to come off and would need to be disassembled to be cleaned. (1) bolt on exhaust and (2) bolts lower on the cylinder heads feel like they’ll be b*tchy to remove, with a high snap! probability.

Expect to break some bolt's heads off due to extreme salt/crap seizure, The dilemma is : break some bolts removing the cylinder head and exhaust covers to manually clean and decarbon both or don't make a thing and keep having peeing issues that will lead to a future overheat. Better remove the whole powerhead from the pan, there are water passages located under it. Broken head bolts can be removed at a machine shop at a relative cheap cost.

Happy Boating​

 

[DIY1111]

Update: All is working. Took her for a Bay test - water flowing perfectly.

Due to the fact that ‘Mickey Mouse ears’ can’t be used to flush this engine, I used a large garbage pail filled with water. THIS WAS THE PROBLEM;

At neutral/ idle, the water flowed from telltale perfectly. When put in gear, the cavitation from prop caused air to get sucked into the impeller housing and once that happened - the impeller, even when engine put back in neutral/idle, could NOT purge itself of the air. The tell tale and water flow would stop, the engine would start to overheat.

When I backflowed water into the exhaust plate / telltale water barb connection, via a reduced garden hose, the telltale and waterflow started to flow again because I was purging the impeller housing with water….

This was frustrating to troubleshoot because my brain could not imagine why the impeller could not purge air… I started to think more sinister problems, ie clogged water passages.

Hope this helps someone down the road…

 

[Sea Rider]

Update: All is working. Took her for a Bay test - water flowing perfectly.

You need to flush any motor with an adequate flushing method for that given motor, if impossible to flush with muffs, use a deep barrel filled with sufficient water level or a flushing port with a hose adapter if having one...

Happy Boating​

 

[DIY1111]

Barrel was plenty deep, about 3’ deep x 2.5’ wide, but not when prop moving… the flushing port would have been forced water and I wanted to see how water pump was working. You’d need a real test tank - oval shaped, or a test prop, two things I don’t have…