What is too hot for a 3.0LX mercruiser (1996)

[sltintexas]

I understand that optimal temp is 143degrees. Mine is running about 165. Instead of tearing down in the middle of boating season is it OK to run it like that? How hot is too hot?

 

[Reel Poor]

Re: What is too hot for a 3.0LX mercruiser (1996)

Since electric gauges in general are not always acurate they serve as a great reference point. "If", 165 is what it has always run you should be good to go.

 

[Don S]

Re: What is too hot for a 3.0LX mercruiser (1996)

That new an engine, you should be running a 160? thermostat, and optimal temp is not 143?.

143? is the opening temp of the older 3.0L thermostats.

 

[sltintexas]

Re: What is too hot for a 3.0LX mercruiser (1996)

It used to run 140ish. Starting last summer it starting showing higher. I replaced impeller and housing and put a few different thermostats on it. They were all 143 thermostats but I thought maybe one was bad. It always runs right on 165-ish. It run so consistently 165 it almost seems like its made to. I am really thinking it may be a faulty reading but have done no investigation.

 

[sltintexas]

Re: What is too hot for a 3.0LX mercruiser (1996)

Great, thx Don. I'll keep on trucking then.

 

[Don S]

Re: What is too hot for a 3.0LX mercruiser (1996)

It used to run 140ish. Starting last summer it starting showing higher. I replaced impeller and housing and put a few different thermostats on it. They were all 143 thermostats but I thought maybe one was bad.

If you have a 143? thermostat in it, and it used to run cooler, then something else is happening.

 

[aerobat]

Re: What is too hot for a 3.0LX mercruiser (1996)

I understand that optimal temp is 143degrees. Mine is running about 165. Instead of tearing down in the middle of boating season is it OK to run it like that? How hot is too hot?

i have a volvo 3.0 GS and it runs 160-165 as well. the thermostat opens like don says at 160 . enjoy boating, there is nothing wrong .

 

[Don S]

Re: What is too hot for a 3.0LX mercruiser (1996)

i have a volvo 3.0 GS and it runs 160-165 as well. the thermostat opens like don says at 160 . enjoy boating, there is nothing wrong .

His temp isn't high enough to hurt the engine, let's put it that way. When an engine with a 143? thermostat normally runs at 140?, then suddenly starts running 25? hotter, trust me, something is wrong.

 

[aerobat]

Re: What is too hot for a 3.0LX mercruiser (1996)

His temp isn't high enough to hurt the engine, let's put it that way. When an engine with a 143? thermostat normally runs at 140?, then suddenly starts running 25? hotter, trust me, something is wrong.

don- he stated that he changed the thermostat - maybe he just put a 160 tstat in and thats the reason for the secret ?


when nothing would be changed i fully agree that a sudden temp rise should always be an eye opener.

 

[Don S]

Re: What is too hot for a 3.0LX mercruiser (1996)

don- he stated that he changed the thermostat - maybe he just put a 160 tstat in and thats the reason for the secret ?

True. he did replace them, but all of them were 143? stats, according to his post.

I replaced impeller and housing and put a few different thermostats on it. They were all 143 thermostats but I thought maybe one was bad.

 

[palace]

Re: What is too hot for a 3.0LX mercruiser (1996)

So we were running at 140's now running in the 160's. Thermostat does one or two things when they go. Get stuck open = running cooler than normal or stuck closed overheating or running hot. Since we changed out the stat's several times. Maybe the circulating water pump is going or a chunk of cast flew off like a clot and is stuck in the block or manifolds some were? If this is all ok then start looking at temp sensor, wiring and guages. There is not much left on cooling system.

 

[sltintexas]

Re: What is too hot for a 3.0LX mercruiser (1996)

I was mainly asking if it was running hot enough to worry about now, or can I wait a while.

but since a few have asked what all I did, here goes.

Last year my boat would run in the 140's. When I'd stop to let in a tuber I'd stop the motor, turn it back on and it was hot, then quickly go down in the 140s. I noticed towards the end of the year it was running in the 150s and maybe get up to 170. I had a spare new 143 degree thermostat so I put that in there. No difference. I put another new 143 degree thermostat in there, no difference. At the end of the season, I changed out impeller & housing and put a water seperating fuel filter, then winterized it and full fluid change out and it sat for winter. Impeller was fully intact with no chunks out of it.

this season the first few trips out I noticed it running in the 160s pretty consistently. Again, it run so consistent at about 165 it is like thats its magic temperature.

As an experiment, I took out the Tstat. It ran cold (below 140 usually). I put TSTAT back in and it run 160s. I think in all, I've put 3 different 143 tstats in there since I had a new spare laying around.

 

[acex008]

Re: What is too hot for a 3.0LX mercruiser (1996)

And you're 110% positive the one in there now is a 143? How do you KNOW it's a 143?

 

[sltintexas]

Re: What is too hot for a 3.0LX mercruiser (1996)

And you're 110% positive the one in there now is a 143? How do you KNOW it's a 143?

I'm 95% sure. I do know that the packaging on the latest one said 14x on it. I do know the old ones were stamped with 14x on it. I don't remember looking at the latest one to see if it was stamped with 14x but I know the packaging said that. I can pull it this weekend and verify. Good thing I bought a bunch of gaskets.