overheat after extended idle

[david901]

1995 Mercury 175 EFI ECU. Engine gets hot after idling around for a while. Cools back down when running on plane. Water tell-tale spits and spurts the whole time. Put new water pump and thermostat on. Still had problem. Put new gasket between powerhead and mid section thinking it may have water passage partialy blocked. Still have same problem. Any ideas what else could be causing this problem?

 

[gss036]

Re: overheat after extended idle

Mercury 2 stroke engines do not like to idle for long periods on time. If you increase you idle a little it will cool down a little bit. You may want to check to make sure the poppet valve is operating properly. If it is stuck open, you will definitely run on the warm side. Did the buzzer sound? If not you were not that hot.

 

[david901]

Re: overheat after extended idle

yes the buzzer did sound. The motor gets extremely hot to the touch even after sitting 30 minutes or so. What does the poppet valve do and where is it and how to test it? Thanks for your help!

 

[gss036]

Re: overheat after extended idle

The poppet valve is located on the lower starboard side of the block and it's purpose is to control the water flow in the block. If it is stuck open, then too much water flows through the block and does not provide the cooling needed. It has 4 small bolts if it is a figure eight(8) laying sideways. It has 3 gaskets , couple washer of washers and a diaphragm, simple to fix, just do not strip out the small 3/8" screw/bolt heads and remember you are working with aluminum. There is not a kit so you would need to buy individual parts. The last time I did one, it was under $30.00 for parts.

 

[david901]

Re: overheat after extended idle

Thanks. Ill check that out.