Hot temps at low RPM's

[Silversound]

1993 Mercury XRi 150
I changed the entire water pump a few days ago. At high RPM's above 3000k the pressure goes up to 10psi. At WOT is will go up to 16psi but if I try to go at a slower speed under 3000k the motor starts to heat all the way up to 180 degrees. If I keep a speed over 3500 rpm the temperature stays at 140-150 degrees. Any suggestions.

Thanks

 

[Bifflefan]

Re: Hot temps at low RPM's

Are you sure you put the right one back in?

 

[Silversound]

Re: Hot temps at low RPM's

Are you sure you put the right one back in?

the water pump kit? I guess it is, I got it from a repair shop and they are really knowledgeable about Mercury.

When I take off to get on step the pressure gauge stays really low until I get to 3000rpm or over.

 

[Faztbullet]

Re: Hot temps at low RPM's

Was the old impeller missing any pieces?? Is the water stream at idle strong or weak?

 

[Silversound]

Re: Hot temps at low RPM's

Was the old impeller missing any pieces?? Is the water stream at idle strong or weak?

No pieces were missing from the impellor, it had very small cracks. The stream at idle is weaker then higher rpm. The pressure stays low when I take off and you can watch it shoot up to 10psi the minute the tach reaches 3000 rpm

 

[TheFisherman78]

Re: Hot temps at low RPM's

Check your thermostat(s)

 

[sschefer]

Re: Hot temps at low RPM's

The engine has a lean idle. There are a lot of causes but usually its just dirty carbs.

If there is too much gap between the throttle cam and the roller there will be too much advance early on and that will cause it to heat up in the lower rpms but cool down in the higher rpm ranges.

 

[Faztbullet]

Re: Hot temps at low RPM's

Re: Hot temps at low RPM's

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The engine has a lean idle. There are a lot of causes but usually its just dirty carbs.

If there is too much gap between the throttle cam and the roller there will be too much advance early on and that will cause it to heat up in the lower rpms but cool down in the higher rpm ranges.

Steve.. I might agree with ya but its a XRi fuelie and has no carbs. Check the poppet valve to see if a piece of debris has it hung slightly open. That motor should have 1-3 psi on guage at idle and a minium of 12 psi @5000 rpm but pee stream at idle should be solid and fairly strong.

 

[Silversound]

Re: Hot temps at low RPM's

Steve.. I might agree with ya but its a XRi fuelie and has no carbs. Check the poppet valve to see if a piece of debris has it hung slightly open. That motor should have 1-3 psi on guage at idle and a minium of 12 psi @5000 rpm but pee stream at idle should be solid and fairly strong.

Ok I will check the poppet valve. At 5000 I see 14psi sometime a little bit more.

I will check the poppet and post the results. Thanks

 

[Silversound]

Re: Hot temps at low RPM's

Well I checked the poppet valve and even had a technician look at it and he said it looked good. Everything was clean and it appeared to be in good working order. I went and rode the boat and it still does the same thing. I have to be going over 3k rpm to keep the pressure up and to keep from overheating. At 2500 rpm I am only getting around 6psi on the water gauge. I at a loss here, I even pulled the stats and checked them and they are working fine. If I run 3200 and over the motor temp stays at 140-145. At 5000 rpm WOT I have 15-16psi.

 

[k dogg]

Re: Hot temps at low RPM's

did you load the impellor in correctly ( turn the driveshaft clockwise while installing the pump housing)

 

[Silversound]

Re: Hot temps at low RPM's

did you load the impellor in correctly ( turn the driveshaft clockwise while installing the pump housing)

Thanks for the reply.

After I read your post I decided to take the lower unit off again and re-check the water pump. When I installed the new WP kit I installed it back the same way it was from before. I reinstalled the parts and turned the shaft clockwise as you suggested.

I went give the boat a try and man it finally works properly. I am not sure of the exact problem from before but now I have gained more psi at WOT. I now get 20psi at WOT and it did not run hot at a low rpm. I ran the motor at 2200 rpm for quite a while and the temperature stayed normal.

It appears that the main problem was possibly that the impeller was installed wrong. I guess I should have not followed the direction of the previous installer.

Again thanks for the help, this finally solved my cooling issues.

 

[Faztbullet]

Re: Hot temps at low RPM's

I doubt that was problem as the impeller will "flip" itself at high RPM if installed backwards, more possible that water tube seal rolled and blocking output. Glad its fixed!!!

 

[Silversound]

Re: Hot temps at low RPM's

I doubt that was problem as the impeller will "flip" itself at high RPM if installed backwards, more possible that water tube seal rolled and blocking output. Glad its fixed!!!

I am glad you mentioned about the tube seal. I did change that seal also.

Thanks for the reply