temp

[Jim clear]

Question for all.

I have a 2005 150 hp merc xr6. Had over heating problem last year. Found seal that shaft goes through on water pump housing almost gone. Replaced impellar seals and gaskets, popppit valve and thermostats. Everything was fine. Had 14 psi water presuure. Toward the end of the season saw some loss in pressure at idle. First time out this year motor started right up, had good pressure at idle 8 to 10. Then it started to fluctuate up and down, from 4 to 8 at idle. did not open her up but got it up to about 40 and pressure settled in around 10 but no higher. it is not overheating, it sarts to spit water at first then i get a steady stream which tells me the thermostats are ok and opening at 143. There is really no issues but I keep reading that my pressure should be higher. Any info or help.



Thanks

 

[Bob Bourget2]

Your motor has a thermostatically and pressure operated cooling system. The pressure varies greatly with rpm and block temp. Bottom line.....minimum water pressure above 4500 is 15psi. The tell-tail will range from barely a dribble to a scalding hot stream, and anything in between.

If you cannot get above 10psi, there is something wrong. Have another look at the therms, to be sure they are not stuck open partially with some debris. If they look ok, have another look at the pump and poppett.

 

[Jim clear]

Thanks Bob, I was hoping you would answer. I will change out the thermostats tomorrow and then check it out. This really bugs me lol. I will let you know what I find if anything.

 

[Dan Poff]

Is there any documentation that says what water pressure should be at different RPMs?

I have an O8 Z7 with a 150 Opti and I don't think I have ever seen the PSI over 10 even at WOT, but the engine has not overheated or set off any alarms.



I always see a steady pee stream, but I have always wondered if the water pressure was to low, or the guage was not accurate.

 

[Bob Bourget2]

The 2.5L Opti's are different....

at idle {625 rpm} 4-6 PSI.

at WOT {5750 rpm} 11-14 PSI....