2002 225 Optimax - Overheating at idle only

[mskycrz]

I have mercury 2002 225 Optimax temp starts rising only at idle normal temp around 130-135 but at idle it quickly starts rising till alarm sounds around 175 180 .However if i rev engine above 1100 rpm temp quickly starts to drop to normal .I have smartcraft gauge which is very useful because i can watch temp and see how it reacts to rpm change! So I have no problem as long as I not just not sitting there idling. Any thoughts of where to start? The impeller is new within 10 hours. The thermostats appear to function fine when I place them in hot water. No junk clogging them. The telltale shows pretty strong spray at higher rpm's but is fairly low at idle while on the muffs.
Thank you

 

[Kola16]

Is this engine ran through saltwater, sand, or mud?

 

[mskycrz]

Is this engine ran through saltwater, sand, or mud?

nope, none of the above as far as I know.

 

[Kola16]

In that case, I would say it is a stuck/bad poppet valve.

 

[Chris1956]

Idle temp control is managed by the thermostats. Starting at about 2000RPM the poppit valve controls the temp. Therefore, I would check the thermostats.

If the 'stats check out, Mercury motors will overheat at idle, if the bottom part of the waterpump impeller is damaged a bit. They will run cool at fast idle or faster.

 

[mskycrz]

Idle temp control is managed by the thermostats. Starting at about 2000RPM the poppit valve controls the temp. Therefore, I would check the thermostats.

If the 'stats check out, Mercury motors will overheat at idle, if the bottom part of the waterpump impeller is damaged a bit. They will run cool at fast idle or faster.

Ok thank you. When I get time Wednesday I will take that apart and look for damage.

 

[Faztbullet]

Check the strainer in the exhaust plate also

 

[mskycrz]

It ended up being an easy fix. Removed to check impeller and the gasket was ripped, replaced the gasket and reinstalled, perfect now. Thank you for the suggestions.