Correct engine temp.?

hezzy602 · Jun 21, 2009

I was running my boat with the ear muff things today and they slipped off for about a minute or two. I quickly turned off the boat and looked at where the water enters the stern drive and saw a little smoke leaving it. I put the ear muffs back on turned the water on quickly.
So now my question--Is my impeller ruined? It was a brand new one with zero hours on it. My boats temp is about 170 degress F while at about half throttle (not n the water, with muffs on) and about 210 degress when idling. My max reading is about 250 degress.
So do i need a new one (impeller) or will i be ok??
Whats the normal engine temp?
I have a 1985 VIP 18.5' w/ MCM205 mercruiser 262cid 4.3L, MR or alpha sterndrive but not sure.

hezzy602 · Jun 21, 2009

Re: Correct engine temp.?

More info--my timming is at about 10 degress btdc, manual says 8. I do not have a thermostat in right now.
Ive been reading other postings on engine temps all night and am getting mixed info?

Some say engine should run no hotter than about 180 and others say 200 degress.
And yes i will be putting back in a new thermostat, after reading other posts. What temp thermo should i pick up for the boat???
I am also going to go get a infrared gun tomorrow and check the risers and other engine locations. What temperature should they be at??

slasmith1 · Jun 21, 2009

Re: Correct engine temp.?

is it fresh water cooled (heat exchanger) or raw water cooled?

hezzy602 · Jun 22, 2009

Re: Correct engine temp.?

Ummmm not real sure, how can i tell?

But if I'm correct its raw water because i dont have a radiator, sound right?

zinc · Jun 22, 2009

Re: Correct engine temp.?

hezzy602 said:
More info--my timming is at about 10 degress btdc, manual says 8. I do not have a thermostat in right now.
Ive been reading other postings on engine temps all night and am getting mixed info? Some say engine should run no hotter than about 180 and others say 200 degress.
And yes i will be putting back in a new thermostat, after reading other posts. What temp thermo should i pick up for the boat???
I am also going to go get a infrared gun tomorrow and check the risers and other engine locations. What temperature should they be at??

Raw water cooling, 140 to 150 degrees, fresh water cooling 185 to 195 degrees.

Bondo · Jun 22, 2009

Re: Correct engine temp.?

So now my question--Is my impeller ruined?

Yes...

JustJason · Jun 22, 2009

Re: Correct engine temp.?

So now my question--Is my impeller ruined?

Yes... Absolutely. They only last 10-15 seconds with no water.

slipped off for about a minute or two

Imagine smoking the rear tires on a car for a full 2 minutes... they'd be toast to. Becaust thats what is happening.

My max reading is about 250 degress

That would be an overheat... depending on how long it was running that hot you may have toasted the flappers and the rubbers on the exhaust.

Top of the morning to ya Bill.

hezzy602 · Jun 22, 2009

Re: Correct engine temp.?

Ok today I'm going replaces my impeller, again! So my gauge should read no higher than what, 160, with muffs on?

Dshow · Jun 22, 2009

Re: Correct engine temp.?

The temp gages in a boat aren't real accurate, but my thermostat opens around 160. If my gage ever gets about 175, in investigate the issue. 200+ is the danger zone...

JustJason · Jun 22, 2009

Re: Correct engine temp.?

160 tops... remember... on the muffs with a good water supply, don't rev the engine over anything more than a fast idle for a minute tops.

hezzy602 · Jun 22, 2009

Re: Correct engine temp.?

Ok so i just replaced my impeller and put back in a brand new 143 degree thermo. I checked both exhaust flappers both are in great condition. It runs hotter than what it was with the old impeller and no thermo!?!?!? So i took back out the thermo and with the new impeller the engine is running very cool, no higher than about 150 degrees?!?! BUT i thought all you guys say a thermo is a MUST, than why is my engine running cooler with it out???

*With new impeller and 143 degree thermo it reads about 180-195 degrees
*With new impeller and NO thermostat it reads no hotter than 150.

So i left the thermo out, seems like common sense to leave it out if its running cooler, right bond-0, common sense, right?!?!?!

Last question is, my starboard side exhaust riser, elbow, is hotter than the other side, where is a good place to start looking for clogs or blockage??? What should be surface temp reading on a infrared gun??

zinc · Jun 22, 2009

Re: Correct engine temp.?

hezzy602 said:
Ok so i just replaced my impeller and put back in a brand new 143 degree thermo. I checked both exhaust flappers both are in great condition. It runs hotter than what it was with the old impeller and no thermo!?!?!? So i took back out the thermo and with the new impeller the engine is running very cool, no higher than about 150 degrees?!?! BUT i thought all you guys say a thermo is a MUST, than why is my engine running cooler with it out???

*With new impeller and 143 degree thermo it reads about 180-195 degrees
*With new impeller and NO thermostat it reads no hotter than 150.

So i left the thermo out, seems like common sense to leave it out if its running cooler, right bond-0, common sense, right?!?!?!

Last question is, my starboard side exhaust riser, elbow, is hotter than the other side, where is a good place to start looking for clogs or blockage??? What should be surface temp reading on a infrared gun??

With the thermostat out, look closely on the end of it, in the center, they stamp the temperature as to which that stat will open at,should have 140 stamped there, if it says 195, then there's your problem.....im thinking someone might have switch it with the wrong one.
As for the rise, how much hotter then the other one??

cr2k · Jun 22, 2009

Re: Correct engine temp.?

With thermo out you will run cooler. Because there is a lot of water going through the system.

Problem with that...if engine never comes up to temp damage can occur form pistons not fully expanded causing uneven wear on cyls. block and heads not getting up to temp, warps due to uneven heating. etc. stat Good!

engine will run hotter with thermo because it is held in the block longer to achieve a more even temp. which is determined to be proper operating temp for that engine.

Did you get ALL of the old impeller out of the system? do you have ALL the pieces to put it together.

If not most likely impeller pieces are lodged in the heat exchanger restricting flow.

cr2k · Jun 22, 2009

Re: Correct engine temp.?

Oh yeah, for a 143* thermo about 150-160 for a 160* around 170-190ish

210 2 high.

As was stated eariler, boat temp gauges are notoriously dis functional.
Get a IR heat gun and point at the thermo housing when you feel it get warmer as in the stat opening.

Overheating Gremlins are tricky devils.
We are currently chasing one that blows the hose form the thermostat housing to the circulation pump splits it wide open. (sea water cooling system). So far I have found a piece of old impeller cutting off the bypass water to the manifold (around the thermo) and an old flapper down the exhaust tube at the transom. Possibly restricting the exhaust which since the mix could increase the water pressure. This could be the problem. waiting for one more gasket to put it together and find out.

hezzy602 · Jun 23, 2009

Re: Correct engine temp.?

so i took my boat to the lake today and ran it for about 20-30 mins. Used an infrared gun and these are my readings starboard exhaust riser and elbow is 170 degrees, port side is at 140 degrees, right where my temp sender is 140 degrees. The only reading that was higher than about 140-150 was my starboard side exhaust riser and elbow. So like you were saying some of my old impeller might be blocking some water flow?? What else should i check??
I dont have a heat exchange so i shouldnt look there for the old impeller pieces? or do i have a heat exchanger (i dont have a radiator)

zinc · Jun 24, 2009

Re: Correct engine temp.?

hezzy602 said:
so i took my boat to the lake today and ran it for about 20-30 mins. Used an infrared gun and these are my readings starboard exhaust riser and elbow is 170 degrees, port side is at 140 degrees, right where my temp sender is 140 degrees. The only reading that was higher than about 140-150 was my starboard side exhaust riser and elbow. So like you were saying some of my old impeller might be blocking some water flow?? What else should i check??
I dont have a heat exchange so i shouldnt look there for the old impeller pieces? or do i have a heat exchanger (i dont have a radiator)

(1) Ok; this thread is starting to get tricky, originally we where discussing the water temp with and with out the thermostat in the system,
Did you manage to figure out what was going on there?
(2)An easy way to determine if you have a heat exchanger would be....
Do you have to take a radiator cap off to add antifreeze to your cooling system???
"IF NOT" Then you have what is called a RAW WATER cooled engine,,
It picks up water from the river circulates it through the engine block and manifolds and then dumps it back overboard.
(3)Where your water temperature sender is....you said you measured 140 degrees...is that with the thermostat in??
(4) If possible, can you take a picture of the hoses and thermostat housing and post them here so we all can see what you got.....A lot of eyes viewing this thread might see something amiss, so we can steer you in the direction.

hezzy602 · Jun 24, 2009

Re: Correct engine temp.?

I ran it yesterday without the thermo, i know iknow i should have it in but i wanted to see the temps all over the engine with the infrared gun. later today i am going put it back in and take the infrared gun and check the same areas.
OK i for surely have a raw water system.

madurodave · Aug 8, 2009

Re: Correct engine temp.?

I wish I could have seen this followed through. I run 175 degrees with 160tstat. Sometimes when the tstat opens, it drops to 100-110 but climbs back up and hovers around 175. Hottest I have seen it is 185.

Starboard riser is hotter than port. Flushed all lines, replaced tstat, impeller and sending unit (bad anyway). Maybe some blockage in the startboard elbow but unless I get hotter that 180-190 this boating season, I will wait until winter to tear into in the garage.

Correct engine temp.?

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