Mercruiser 230 Cooling system issues

Gentlemen, I have a Mercruiser230 Chev 305 with a Alpha 1 lower unit. Had it started up, water running though all the lines with the muffs on, than, all of a sudden it overheated and I cannot get water from my muffs back up to the T stat housing. Impeller maybe? Can it just "Go bad" all of a sudden like that? Also, I am not confident that the cooling lines coming and going from the t stat housing are correct. I replaced the PS cooler this spring and am confident that is not leaking, and it is plugged in correctly to the Tstat housing, with the line going to the engines water pump across from it, my concern is with the lines on the top of the housing, which one where? Any help guys? A diagram of the cooling routing lines would be beneficial at this point.

Re: Mercruiser 230 Cooling system issues

The first place I'd look at is the impeller.
You will need to post the engine serial number, someone might post a link to the maintenance manual. Look in the cooling system section for the diagram of the engine's cooling hose routing.

Re: Mercruiser 230 Cooling system issues

engine serial # a341338
I've also taken the t-stat completly out of the housing and reinstalled the housing empty to ensure water could pass and.... nothing

Re: Mercruiser 230 Cooling system issues

I've also taken the t-stat completly out of the housing and reinstalled the housing empty to ensure water could pass and....

Click to expand...

Ayuh,... That alone will cause spot overheats...
The t-stat helps direct the water to where it's gotta go..

Re: Mercruiser 230 Cooling system issues

I thought by taking the Tstat out I would ensure adequate water flow to all components, I was worried the stat was maybe stuck closed?

Re: Mercruiser 230 Cooling system issues

No the stat manages where the water goes. Water always goes out through the exhaust, but when the stat is cold very little water goes through the block & heads.

Re: Mercruiser 230 Cooling system issues

How long should it take for my exhaust hoses to fill with water after I have had the system drained? Even with the thermostat back in and the housing secured I have no flow coming out of any of the four ports on the top of the housing, it's like they're dry. The front two have a spring and ball assembly in them, and I am just lost as to what lines go where, and why I all of a sudden can't get any water. My risers are getting extremely hot very quickly, but my temp gauge hasn't come up, note.... I have not run the engine for more than 25 sec with no water flowing though, scared of heating the risers and manifolds with no water in them.