How hot is too hot?

[Friscoboater]

I just saw a post that scared me. He said that 200 was too hot for a boat. For those of you that have not seen my thread, I just rebuilt my boat. New 5.7 new manifolds risers and impeller. When it was really hot out (104) my engine would touch 200 when we were really hammering on it or a wot run across the lake. Once you slowed down it went back to the 140 to 160 range. I can still put my hands on the risers. This past weekend we had a big cold front that came through and the water is cooler. The boat never gets over 180 now. Do I have an issue?

 

[bigdan1]

Re: How hot is too hot?

no ,
all normal to me ......

at wot the engine goes warmer : normal .

do you have only the impeller in the outdrive to bring water in engine ?
if so yes it `s normal to raise to 190 on hard drive !

 

[Alpheus]

Re: How hot is too hot?

I have a 160 Thermostat in my boat and it never gets hotter than 160. Check and make sure your thermostat is working correctly. If its stuck open it will cause symptoms of what you are describing...

I have not had an engine with check balls so I did some digging on the check balls and found some info. From what I can see the check balls are used as a relief valve so that when the pressure in the cooliing system gets too high, the valves open and release the water into the risers. If the springs are weak (worn out), the cool water just passes right by them, lowering the pressure and flow in the engine and just dumping the water from the seawater pump right out the risers before it has a chance to cool the engine...

 

[Lou C]

Re: How hot is too hot?

No I don't think that's normal, keep in mind if you have a raw water cooled system, it is not under pressure as a car system is with a 15 lb cap. So water will boil at 212 F and can start boiling in hotter parts of the engine even lower. Coolant/water mix as in closed cooling won't boil till 265F if properly mixed with a good pressure cap. A raw water cooled engine with a 160 stat typically runs from 160-175 if all is well, even at higher speeds. If you get to 200 then you have to find out why. My old 88 OMC 4.3 (original motor, run in fresh for about 10 yrs and last 12 in salt) has never run over 175 with the 160 stat. It gets a new impeller and thermostat each season. The 'stats get sticky in salt water so it's best to just replace em. I check the manifolds/risers every 5 seasons. I'd check to make sure there are no restrictions and your impeller is good. Also it would be good to make sure the thermo housing is OK, don't some Mercs use check balls that can cause trouble with overheating?

 

[wire2]

Re: How hot is too hot?

I have a 160 Thermostat in my boat and it never gets hotter than 160. Check and make sure your thermostat is working correctly. If its stuck open it will cause symptoms of what you are describing...

If it's stuck open, it should never get up to 160?, cool lake water is constantly flowing through the engine.

Now, if it's stuck only partly open, then in might peak with a hot run.

 

[jerryjerry05]

Re: How hot is too hot?

Too hot.It should never get hotter than 160.
Is there a thermostat in the motor.How about restrictions in the Y pipe.Old flappers get stuck there.The right gaskets on the new man/riser?
If yours has check balls make sure they are free.J

 

[natemoore]

Re: How hot is too hot?

water will boil at 212 F and can start boiling in hotter parts of the engine even lower

 

[Cpt D]

Re: How hot is too hot?

I agree with Alpheus. My 4.3 never changes temperatures whether idling or wot. Raw water cooled motors should run pretty consistant temps at all speeds. I think you do have a problem with your cooling system and you are right to be worried about it.

 

[Friscoboater]

Re: How hot is too hot?

Got a 140 tstat and it is working great. I just can't help but think that you will get warmer when you make a high speed run. The tstat opens and your engine will only get as cool as the water will allow. Our lake temps when this was happening was around 92 to 94. I know that sounds high, but we had a really hot summer and this lake is man made and gets HOT!! Once the lake got cooler the temps are back to normal.

 

[sethjon]

Re: How hot is too hot?

I just saw a post that scared me. He said that 200 was too hot for a boat. For those of you that have not seen my thread, I just rebuilt my boat. New 5.7 new manifolds risers and impeller. When it was really hot out (104) my engine would touch 200 when we were really hammering on it or a wot run across the lake. Once you slowed down it went back to the 140 to 160 range. I can still put my hands on the risers. This past weekend we had a big cold front that came through and the water is cooler. The boat never gets over 180 now. Do I have an issue?

200 is definitely too hot. Sounds like a thermostat problem. Pull it out and replace if you have any doubts. If that doesn't correct all the time then check for a blockage.

 

[sethjon]

Re: How hot is too hot?

no ,
all normal to me ......

at wot the engine goes warmer : normal .

do you have only the impeller in the outdrive to bring water in engine ?
if so yes it `s normal to raise to 190 on hard drive !

If everything is good then a temp rise of that much is not normal.

 

[Friscoboater]

Re: How hot is too hot?

My wife says I am not correct in what I saw on the temp gauge. She says the only time it goes that high is when you have been driving and you stop the engine. The water then is not moving through the engine and when I leave the ignition you can see the gauge go up . Once you start it it goes down to normal. She states that when running it was between 160 and 180. I will have to test it out again this weekend and let you know. If it is getting that hot, then I need to back off the timing a little.

Remember I am running higher compression, hotter cam, and a re-jetted carb. Everything on this thing is new.

 

[Philster]

Re: How hot is too hot?

T-stat confusion. A 160 t-stat opens at 160, but it powerless to keep an engine at 160. It's the rest of the cooling system's job to keep it at 160. T-stats aren't much about cooling anything. Essentially, they're about warming things up.

They permit the cooling process to begin.

160 t-stat and you drive hard and long and in warm waters, I'd question my sender if she never got above 160 on the gauge. 160-180 is very normal on a 160 t-stat. You have to watch. Over time, as pieces age/wear, she'll start getting to 185+. I'd start worrying at that point.

Is 185 ok? Sure, nothing will boil/melt, but you just reduced the room for error and you know something needs a checkin'.

With a 160 t-stat, I'd expect the temps to dip below 160 now and then, in which case the t-stat will close, and as soon as 160 is reached again, she'll open.

 

[Friscoboater]

Re: How hot is too hot?

Here is the report from last weekend. She ran no hotter than 170 after a 10 minute run at WOT. When we were water skiing it stayed at or below 160. The only time it climbed was when the engine was off, and that makes sense.

 

[paultjohnson]

Re: How hot is too hot?

Im surprised to see so many people state the temps vary so much on there boats I have an 86 4.3 runnin a 143 deg stat. My gauge rarely , if ever is out of the 140s either way, once it warms up. Doesnt matter if its on muffs, in the lake , If the water temp is 40 or 85. If i am at Idle, skiing or WOT. It just stays where its supposed to. Guess im just lucky FYI

 

[Evinrude Boater]

Re: How hot is too hot?

Im surprised to see so many people state the temps vary so much on there boats I have an 86 4.3 runnin a 143 deg stat. My gauge rarely , if ever is out of the 140s either way, once it warms up. Doesnt matter if its on muffs, in the lake , If the water temp is 40 or 85. If i am at Idle, skiing or WOT. It just stays where its supposed to. Guess im just lucky FYI

I'm with ya Johnson. My boat is the same, rock solid temp gauge.

 

[bigskiohio]

Re: How hot is too hot?

my 140 thermostat runs 140 t0 160, plus never shut down a engine after wot let it idle for a couple of minutes befor turning off.

 

[QC]

Re: How hot is too hot?

Who says all your gauges are right? Mine is 15 degrees off . . .

Philster is dead on with respect to the role of a thermostat. Most range from their opening temp (on stat) to around 12 degrees above that for fully open i.e. a 160* would be fully open at 172*.

 

[paultjohnson]

Re: How hot is too hot?

I'm with ya Johnson. My boat is the same, rock solid temp gauge.

Dont ya love it!

 

[JoLin]

Re: How hot is too hot?

I'm with ya Johnson. My boat is the same, rock solid temp gauge.

Make me # 3. My temp gauge isn't exact (dopey scale), but it hangs right around 160 when I'm warmed up. NEVER moves.