Is my 4.3L Overheating?

[Boatsrneat]

I have a 2000 4.3L, Carbed, 190 horse, open cooling system, alpha 1 gen2 o/d. I havent had the boat that long and noticed at normal operating, temp guage is around 175 +/- 5. Cruising, trolling, and idle...about the same. Is this a normal op temp? A lot of people I ask this question think its to hot. I then decided to replace the impeller and thermostat. While doing that, I noticed the thermostat is a 160 degree stat... Seems 175 is not that bad. After some research, it sounds like the older 4.3's used a 140 stat and maybe thats why people I talked to thought it was hot? Anywhay, after the stat and impeller change, no change in running temp. Any comments?

Thanks,
Steve

 

[QC]

Re: Is my 4.3L Overheating?

Well my guess is that your gauge is slightly off. Open systems should run pretty close to the thermostat rating . . . If it stays pretty close all of the time though, I wouldn't worry about it. My current gauge reads about 15 degrees high, I know where it sits and you are really only looking for deviation.

 

[Haut Medoc]

Re: Is my 4.3L Overheating?

With a 160* stat, I would think it would run cooler, but you are not overheating.....
Over 180* I'd be changing to the 143*......
How old are the man/risers?........
If they are original, they are near the end of their service life, esp if you boat in salt......​

 

[Boatsrneat]

Re: Is my 4.3L Overheating?

Risers are original, the engine/boat has 48 Hrs on it. Runs great. Do the risers rust up or somthing?

Good point about the guage accuracy. I'm going to bring home my thermo temp gun and measure at the sending unit. Guess that will be the true test.

Steve

 

[QC]

Re: Is my 4.3L Overheating?

I'm going to bring home my thermo temp gun and measure at the sending unit. Guess that will be the true test.

Puuuuurrrrrfect . . .

Bro Haut,

I am surprised you kinda recommend a lower degree stat for any overheat. Thermostats only control minimum temp, they have nothing to do with max Sooo if he is running hot, going to the 143 would only insure higher temp swings from cold to hot and back. This assumes that the original is opening completely, but he just replaced it . . .

 

[Haut Medoc]

Re: Is my 4.3L Overheating?

Puuuuurrrrrfect . . .

Bro Haut,

I am surprised you kinda recommend a lower degree stat for any overheat. Thermostats only control minimum temp, they have nothing to do with max Sooo if he is running hot, going to the 143 would only insure higher temp swings from cold to hot and back. This assumes that the original is opening completely, but he just replaced it . . .

It's not an over heat.....
I did mention the mans/risers.....
I'd check the temp as suggested with the gun to verify.....
But at seven old, I would suspect that the risers need to be looked at.....
& as far as I know, all standard cooling on Mercs is supposed to have the 143* stat.....

 

[newtoboats39]

Re: Is my 4.3L Overheating?

I'm no expert but a while back I had the same question. It seems to me that a 160deg thermostat means that it starts opening at 160 and would be fully open at 180ish wouldn't that imply that the top acceptable temp would be closer to 180 than 160?

 

[QC]

Re: Is my 4.3L Overheating?

OK, let me clarify. I thought Bro Haut suggested that if it was running over 180* maybe try the 143* stat. That seems like suggesting that it will help cool it down . . . Also, yes, 160* is the opening temp, most stats fully open around 10 - 12 degrees higher, but . . . . I understood that at idle he was seeing around 175 (gauge), but that would not be "fully open".

 

[Haut Medoc]

Re: Is my 4.3L Overheating?

Well, it would cool it down......​

 

[QC]

Re: Is my 4.3L Overheating?

No, it would slow overheating . . . Maybe this is the result of the new Dockside rules . . .

 

[Haut Medoc]

Re: Is my 4.3L Overheating?

If you say so......
If you are running in salt water, you should be running the colder stat anyway......​

 

[Boatsrneat]

Re: Is my 4.3L Overheating?

I live near Chicago, strictly local lakes. I'm an auto machanic, and I know people think that auto mechanics THINK they know marine engines... and for the most part, thats correct. My co workers think they know it all too. One thing we were all discussing at lunch was...175 for an all cast iron engine seems pretty normal. We also agreed that "auto" engines seem to run 10-15 above a specified stat degree rating. The reason for this question in the first place was to get a "boaters" opinion. Auto mechanics know about engines, and there IS a lot that is similar in marine engines, BUUUT it was funny when I/we learned that an impeller was rubber We kept wondering why everyone was so parinoid about running an engine a short while with no water...OOOOhhhhhh...now I see....:redface: As for the thermostat rating, 160 is the correct Quicksilver part. And 160 is what came out, so I'm pretty sure thats what this engine calls for. Anyone have a later model 4.3L carbed Merc? What temp does yours run at?

Steve

 

[DayCruiser]

Re: Is my 4.3L Overheating?

I have a 3.0 mercruiser with a 160 therm. When idleing it will go slightly over 160. When running hard it will do the same. Cruiseing speed it will run around 155. I would think too if its is constant at 175 then the gauge must be off a bit

 

[moser42]

Re: Is my 4.3L Overheating?

I have a 2006 4.3 carb 190hp.
Once warmed up it stays at a solid 180-183.

 

[wca_tim]

Re: Is my 4.3L Overheating?

I have a reman 4.3 4bbl with new manifolds and risers. Checked the temp gauge from 120 to 180. Guage was surprisingly accurate (far as i could read the marks on the gauge, within a couple of degrees over that range). Temp stays consistently between 160 and 165 most of the time. May go up to 170 when running fast (ie.near wot) for a while, but given a few minutes drops back to ca. 160. Also has new (ca. 15 hours) impeller, etc...