200 Mercury running hot at certain rpm

J

jdupree

Petty Officer 2nd Class
Joined
Aug 11, 2006
Messages
185
I have a 1992 200 Mercury. Motor was re-built 2 seasons ago. I have just intalled new impeller, poppitt, t-stats. Motor runs where it should temp wise at WOT and at idle. What is strange, is that if I am trolling between 1200 to 1400 RPM's the temp creeps up to around 190deg and hovers there. If I back off the throttle to 1000rpms it drops and if I give her some gas and get it up to around 2000rpm's she drops. I don't feel like I have a blockage issue, because of the re-build and it runs cool at idle and WOT. This one has me scratching my head. Thanks for any opinions.
 
G

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: 200 Mercury running hot at certain rpm

I think that is normal on the 200 hp Mercs. That is about the same as mine.
Do you have a water pressure guage? That is the best way to moniter the cooling system/water flow.
The overheat heat sender will go off around 220 degrees.
 
J

jdupree

Petty Officer 2nd Class
Joined
Aug 11, 2006
Messages
185
Re: 200 Mercury running hot at certain rpm

Thanks. This is the 1st Mercury I have ever owned. I have heard that the older ones do run on the warm side but I was just a little concerned about 190deg. Just wanted to make sure I am not hurting the motor.

I plan to install a water pressure gauge soon. I am sure I am getting good water pressure with what I have replaced. It is just weird how the temp rises at just that certain rpm range. Thanks.
 
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