Normal Operating Temperature for a 3.0 liter Mercruiser?

[mnowicki]

I was wondering what the normal operating temperature should be on a 3.0 Liter mercrusier 140hp stern drive?

I have a little less than 145 degrees running at 1000 RPM.. Matter of fact I trolled all day on Saturday (like 12 hrs) at 1000-1100 rpm and the temp gauge never moved from that.. Picked up and ran in running 3000 rpms for approx 15 to 20 minutes and the temp gauge rose to 175 degrees...
Is this normal or is there something wrong? Should it be approx. 145 degree's all the time.. ????

any input would be greatly appreciated..

Thanks
Mark

 

[Bondo]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

Ayuh,.... Welcome Aboard,...

Unless you've done it recently,...
Change the Impeller...

 

[airshot]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

My 140 hangs at 125 degrees all the time, idle or running. As well as impellor, change thermostat,
make sure hoses are not pinched or clogged.

Airshot

 

[CobiaXL]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

My 140 hangs at 125 degrees all the time, idle or running. As well as impellor, change thermostat,
make sure hoses are not pinched or clogged.

Airshot

I'd say your temp gauge needs a good tapping on.My 140 runs 150 idle and 165-170 when running at 4000rpms

 

[conk3416]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

Normal operating temperature should be between 140 and 170 degrees. And it should be at that at all times. I agree with bond-o that you should look into replacing the impeller and also the thermostat. But running at 175 will not hurt anything. If you are not going to replace those things right away keep a close eye on it and dont let it get above 200 degrees.

 

[Rocky_Road]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

My 3.0L (circa 2005) has always ran just a 'tick' over 175, and remains there after every new impeller. Since my OEM thermostat is a 160 degree, this is exactly what I would expect.

Happy boating!

 

[mnowicki]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

Thanks guys... I was planning on changing out the impellor becuause I really don't know how old it is... Just bought the boat in the fall and this is my first year with it...This is the 5th trip with it and this is the first time I've seen the temp go up... but then it's the first time I've ran that far and long at the higher rpm's.. Not too mention the water temps were up and it was 90 degree's that day..

Just was trying to get a feel for how urgent it is to do it...

 

[JWebber]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

My 3.0L (circa 2005) has always ran just a 'tick' over 175, and remains there after every new impeller. Since my OEM thermostat is a 160 degree, this is exactly what I would expect.

Happy boating!

Same here!

 

[mnowicki]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

Just thought I would post up a reply and update which might help someone else..... Impellor changed and did not really make any differenece.. Although Impellor looked pretty bad... But replaced the thermostat and it made a huge difference,,, Don't think the thermostat was really working right??? now it is at 140 when warmed up and pretty much like that all the time...slightly higher when running at 3000 RPMS.... Now it looks normal and pretty much what I would expect...

Thanks for the feedback.

 

[mirrordog]

Re: Normal Operating Temperature for a 3.0 liter Mercruiser?

Just thought I would post up a reply and update which might help someone else..... Impellor changed and did not really make any differenece.. Although Impellor looked pretty bad... But replaced the thermostat and it made a huge difference,,, Don't think the thermostat was really working right??? now it is at 140 when warmed up and pretty much like that all the time...slightly higher when running at 3000 RPMS.... Now it looks normal and pretty much what I would expect...

Thanks for the feedback.

New member and new boater ... my 3.0 mercruiser is overheating and I want to change the stat; however, I can't find any info. on what temp. of stat to purchase. Can you help?