90hp 2 stroke exhaust gas in water jacket

[brian3006]

I have a 2001 90TLR. motor runs good. I was doing maint. on the thermostat yesterday and after scraping some salt off of the lip, I hooked up the water and started the engine just to let water pump out of the hole to flush the debris out. I Just let it run 10 seconds or so, then turned it off. That is when I noticed exhaust gas swirling up through the thermostat hole...Put everything back together and run it on the muffs with no issues.
My main concern obviously is that if exhaust can get into the water, can water get into the exhaust Ie:-cylinders... Got to thinking about which gaskets this could be... naturally head gasket was first to pop up. went out this morning and pulled all the plugs. all of them are oily (not bad, just standard 2-stroke) none of them are wet or clean like water is in the cylinder. did a compression check 125 on all 3 cylinders. let the water run through the flushing adapter for a while, no evidence of water getting into the cylinders. cranked several times with no plugs in..again no evidence of water seeping in.

Finally, I pulled the water hose off where the flushing adapter goes into the block. ran it for about 10 seconds without water hooked up and there was exhaust gas pumping out of the fitting on the block

So can someone point me in the right direction here? What else do I need to be looking at?

[ausnoelm]

First off, never run it without water, your water pump is probably cooked now, the cooling water mixes with the exhaust as it exits the motor.

[Bluefish]

Sounds normal as stated by ausnoeim, Hot gasses taking the path of least resistance your open T-stat instead of down the leg and out the prop.

[99yam40]

that is my thoughts also,
the heavier water drains out the bottom and the hot gases float upward

[brian3006]

Good deal. Thanks for the information. I have never really worked on the midsection of an outboard before, wasn't sure if the two truly mixed together or if they were two separate compartments that both just exit at the lower unit.

I usually never run one without water hooked up. ( I Use to have a barrel that I would prefer to submerge the motor in, but a hurricane blew it away this past fall) As for the impeller, I have a new one sitting here waiting for the snow and ice to melt anyhow.