85 mercury 90 t o p cooling problems

[mail_man]

OK the run down. It started running warm at idle. Changed the whole wp still ran warm with week stream.so I pulled pwr head to check water tube fore cracks everything is good there put it back together with new gaskets. OK so now we have new pump good seal at pwr head good tube but still runs warn at idle. Oh and I flushed head wile all this was a part. Any idea on this heating problem

 

[Bosunsmate]

Re: 85 mercury 90 t o p cooling problems

Thermostat perhaps...............

 

[mail_man]

Re: 85 mercury 90 t o p cooling problems

Thermostat perhaps...............

If I'm not mistaken the mid 80 inline 6's dose not have t-stats.

 

[Bosunsmate]

Re: 85 mercury 90 t o p cooling problems

ok not sure myself.
if it doesnt how hot is it getting?
Leak into exhaust housing perhaps

 

[oldman570]

Re: 85 mercury 90 t o p cooling problems

You should check the inner divider exhaust plate for bad gaskets or cracked/holes in the plate. Also check the lower exhaust plate between the power head and the midsection for carbon buildup that could cause a restriction of the exhaust/water flow. This can cause the water flow to be less than what is needed. If you have a fuel pump pressure gage, you can test the water pressure of the water pump using it with a barb fitting in the tail tell hose or on the head water jacket, where a threaded brass plug is , to check the water pressure with the motor idling in the water and not on muffs. A new pump will often be between 3-5 lbs. at idle, and will rise when RPM's is increased.
JMO
Oldman570