496 ho closed cooling system - 180 temp open throttle? 200 temp idle?

2003 playcraft tritoon 2700 xtreme*
496HO closed cooling*
bravo x drive
300 hours

just had impeller changed (housing good)
thermostat changed

I didnt pay close attention to the first couple trips after change. But now I'm running 180 to 185 open throttle. Almost 200 at idle. No temperature alarm goes off. Are these normal temps for a closed system? I'm not sure if I was ever running 160 before the impeller change(new to boat)

starboard thru hull exhaust has just a small steady stream... when port exhaust is spitting out a lot.*

could it be a "flapper" causing this temperature issue? Can you tell if flapper is still in place and functioning be doing something something? Can you see flapper bu looking into thru hull exhaust?

The thermostat temperature is a 160 degrees so generally the most you "may" see on the gauge depended on all components used could be right around 175ish degrees....While max would be 179 from past experience.... You'll want to get yourself an infrared temperature gun from someplace like harbor fright, etc., and ensure your temperatures are within specs of normal and compare what the gauge is actually saying.

Since you may not be setting off an overheat alarm (that you know of "yet") which if the warning horn system is working correctly/connected, the warning horn system should sound off right round 196 degrees if the engine is truly reaching 200 degrees which again you need to verify the temp and confirm if the warning horn system is working correctly too.

https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465.html

You may also want to try removing both sides of the heat exchanger covers to make sure the internal cooling passages are not blocked up....See item numbers 32 and 33 which will be found on both sides of the heat exchanger,
http://www.marineengine.com/parts/m.../0m687083-thru-0w059999/closed-cooling-system
http://www.marineengine.com/parts/m...rts/496-mag-base-model/0m687083-thru-0w059999

Also be-sure to cover up the lower water pickup on the stern drive nose cone area if you also have the lower stern drive unit "side" water pickups too and are using the side water pickups to run/flush the engine on the garden hose at home.....If your drives has both water pickups and you're only using one of the pickups, the other pickup is sucking air and causing damage to the new or old impeller.

Is your exhaust flow system only through hull exhaust or through prop exhaust too using a Y pipe type configuration ?, http://www.psepmarineparts.biz/store/mercruiser_exhaust_pipes.htm

There are lot's of conditions that could make this design engine temperature run warmer or even hotter than normal but the first step is to verify the temp is actually getting to what the gauge is saying as the gauge or temp sending unit may be defective especially since this boat is still sort of new to you and again the warning horn didn't sound off that you know of.

Here's the reasons for the components used remark for gauge fluctuation and the importance of temp verification, https://www.jamestowndistributors.com/userportal/document.do?docId=842

In addition to this excellent information, keep in mind a closed cooling system is pressurized just like on a car. That means the boiling point of the coolant is much higher than the common sea level boiling point of 212F.

boat_tech said:

The thermostat temperature is a 160 degrees so generally the most you "may" see on the gauge depended on all components used could be right around 175ish degrees....While max would be 179 from past experience.... You'll want to get yourself an infrared temperature gun from someplace like harbor fright, etc., and ensure your temperatures are within specs of normal and compare what the gauge is actually saying.

Since you may not be setting off an overheat alarm (that you know of "yet") which if the warning horn system is working correctly/connected, the warning horn system should sound off right round 196 degrees if the engine is truly reaching 200 degrees which again you need to verify the temp and confirm if the warning horn system is working correctly too.

https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465.html

You may also want to try removing both sides of the heat exchanger covers to make sure the internal cooling passages are not blocked up....See item numbers 32 and 33 which will be found on both sides of the heat exchanger,
http://www.marineengine.com/parts/m.../0m687083-thru-0w059999/closed-cooling-system
http://www.marineengine.com/parts/m...rts/496-mag-base-model/0m687083-thru-0w059999

Also be-sure to cover up the lower water pickup on the stern drive nose cone area if you also have the lower stern drive unit "side" water pickups too and are using the side water pickups to run/flush the engine on the garden hose at home.....If your drives has both water pickups and you're only using one of the pickups, the other pickup is sucking air and causing damage to the new or old impeller.

Is your exhaust flow system only through hull exhaust or through prop exhaust too using a Y pipe type configuration ?, http://www.psepmarineparts.biz/store/mercruiser_exhaust_pipes.htm

There are lot's of conditions that could make this design engine temperature run warmer or even hotter than normal but the first step is to verify the temp is actually getting to what the gauge is saying as the gauge or temp sending unit may be defective especially since this boat is still sort of new to you and again the warning horn didn't sound off that you know of.

Here's the reasons for the components used remark for gauge fluctuation and the importance of temp verification, https://www.jamestowndistributors.com/userportal/document.do?docId=842

Click to expand...

Timeline:
bought boat September 2017.
ran boat handful of times.
honestly didnt pay close attention to temp guage*
but I know it was in 160 to 180 range
had it winterized*
shop told me I'd need sea water pump or impeller next year
I'm pretty certain they guaged it by starboard exhaust not pumping out enough water.
spring 2018, pump housing fine, replaced impeller and thermostat- same shop, pretty certain impeller was intact
and of course... not paying close attention...3rd trip out... someone stops me on water and says my port exhaust is pumping alot more than my starboard*
I start watching the temp guage religiously*
it stays a hair above 180 running normal throttle
it jumps to shy under 200 at idle

is the temp guage on my helm showing my block temp?
my heat exchanger, manifolds, risers are on raw water correct? So I'm not seeing the temp of those on the helm temp guage correct?

If I remove those ends of the heat exchanger... is there anything to be careful about? Do I need to flush and how so. Will I need to watch for air getting in?

Also, when I turn my key to start position, I hear the audible beep... assuming that is testing the alarm? Is the alarm set to the guage on the helm or to the ecm on the motor? Could there be a problem with the alarm even though its sounding at start?

boat_tech said:

The thermostat temperature is a 160 degrees so generally the most you "may" see on the gauge depended on all components used could be right around 175ish degrees....While max would be 179 from past experience.... You'll want to get yourself an infrared temperature gun from someplace like harbor fright, etc., and ensure your temperatures are within specs of normal and compare what the gauge is actually saying.

Since you may not be setting off an overheat alarm (that you know of "yet") which if the warning horn system is working correctly/connected, the warning horn system should sound off right round 196 degrees if the engine is truly reaching 200 degrees which again you need to verify the temp and confirm if the warning horn system is working correctly too.

https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465.html

You may also want to try removing both sides of the heat exchanger covers to make sure the internal cooling passages are not blocked up....See item numbers 32 and 33 which will be found on both sides of the heat exchanger,
http://www.marineengine.com/parts/m.../0m687083-thru-0w059999/closed-cooling-system
http://www.marineengine.com/parts/m...rts/496-mag-base-model/0m687083-thru-0w059999

Also be-sure to cover up the lower water pickup on the stern drive nose cone area if you also have the lower stern drive unit "side" water pickups too and are using the side water pickups to run/flush the engine on the garden hose at home.....If your drives has both water pickups and you're only using one of the pickups, the other pickup is sucking air and causing damage to the new or old impeller.

Is your exhaust flow system only through hull exhaust or through prop exhaust too using a Y pipe type configuration ?, http://www.psepmarineparts.biz/store/mercruiser_exhaust_pipes.htm

There are lot's of conditions that could make this design engine temperature run warmer or even hotter than normal but the first step is to verify the temp is actually getting to what the gauge is saying as the gauge or temp sending unit may be defective especially since this boat is still sort of new to you and again the warning horn didn't sound off that you know of.

Here's the reasons for the components used remark for gauge fluctuation and the importance of temp verification, https://www.jamestowndistributors.com/userportal/document.do?docId=842

Click to expand...

I do have corsa exhaust captains call

boat_tech said:

The thermostat temperature is a 160 degrees so generally the most you "may" see on the gauge depended on all components used could be right around 175ish degrees....While max would be 179 from past experience.... You'll want to get yourself an infrared temperature gun from someplace like harbor fright, etc., and ensure your temperatures are within specs of normal and compare what the gauge is actually saying.

Since you may not be setting off an overheat alarm (that you know of "yet") which if the warning horn system is working correctly/connected, the warning horn system should sound off right round 196 degrees if the engine is truly reaching 200 degrees which again you need to verify the temp and confirm if the warning horn system is working correctly too.

https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465.html

You may also want to try removing both sides of the heat exchanger covers to make sure the internal cooling passages are not blocked up....See item numbers 32 and 33 which will be found on both sides of the heat exchanger,
http://www.marineengine.com/parts/m.../0m687083-thru-0w059999/closed-cooling-system
http://www.marineengine.com/parts/m...rts/496-mag-base-model/0m687083-thru-0w059999

Also be-sure to cover up the lower water pickup on the stern drive nose cone area if you also have the lower stern drive unit "side" water pickups too and are using the side water pickups to run/flush the engine on the garden hose at home.....If your drives has both water pickups and you're only using one of the pickups, the other pickup is sucking air and causing damage to the new or old impeller.

Is your exhaust flow system only through hull exhaust or through prop exhaust too using a Y pipe type configuration ?, http://www.psepmarineparts.biz/store/mercruiser_exhaust_pipes.htm

There are lot's of conditions that could make this design engine temperature run warmer or even hotter than normal but the first step is to verify the temp is actually getting to what the gauge is saying as the gauge or temp sending unit may be defective especially since this boat is still sort of new to you and again the warning horn didn't sound off that you know of.

Here's the reasons for the components used remark for gauge fluctuation and the importance of temp verification, https://www.jamestowndistributors.com/userportal/document.do?docId=842

Click to expand...

Update.*

so in the dark this morning I checked the coolant level. It took half gallon. I started it up on water hose. It ran 164 at the thermostat with a infrared gun. Helm guage showd probably 170. I ran it a good 30 mins with captain call on and off if that matters and raising lowering outdrive. And guess what else... its spitting out both tail pipes like normal now.*

just to check myself...

Is thermostat on port side below the heat exchanger? (Long cylinder deal)?

raw water supply coming in from port side underneath? (Read outside temp here)

Is the long cylinder the heat exchanger? It was 88 on ends... *155 where thermostat comes in.... 135 in middle of cylinder. So it was hottest where thermostat goes in...then decreases to starboard side.

the "squashed" chamber that runs with length of heat exchanger cylinder???.... it was 154 the length of it.

the hose coming out of starboard side of heat exchanger/squashed part... was 135 circling back into engine. Is this small hose cooling the block?

port manifold was 114. Starboard was 109.*

what do ya think?*
​​​​​​​I was told that being a half gallon low shouldn't have given me the symptoms of 182 running 195 idling.*

I'm getting ready to test in water

engine thermostat should be on front/top of the engine where the big hose comes out of the manifold, under the "bolt on" hose fitting.

I would say you could have a water circulation pump issue. NOT seawater pump, but the automotive style water pump on the front of the engine... when running, its moving water fast enough to keep it cool, but at an idle, there is not enough circulation thru the block.... and I would get a 160 degree thermostat, 170 max, as the engine bay will be getting extremely hot on a summer day when the engine runs so hot.

centerline said:

engine thermostat should be on front/top of the engine where the big hose comes out of the manifold, under the "bolt on" hose fitting.

I would say you could have a water circulation pump issue. NOT seawater pump, but the automotive style water pump on the front of the engine... when running, its moving water fast enough to keep it cool, but at an idle, there is not enough circulation thru the block.... and I would get a 160 degree thermostat, 170 max, as the engine bay will be getting extremely hot on a summer day when the engine runs so hot.

Click to expand...

Water test.

temp guage on helm was 180 while running.... infrared gun showed 164.

temp guage on helm 190 while idling... infrared gun showed 170.*

water temp is probably 83 degrees..... so I guess I have to take that into.account for the temp difference than on water hose?*

would you still be concerned at 170? Plus that was on one of those 30 dollar ones ar autozone... think that's accurate? I was measuring right at the thermostat. Where would the temp guage on helm ne measuring at? Should I check into more things since the helm temp guage is so high?

03playcraft496HO;n10597052 said:

but I know it was in 160 to 180 range

Click to expand...

That's where you want the temp to be.

replaced impeller and thermostat.

Click to expand...

If the engine continues to run normal temps after adding coolant, then chances are you had some air in the coolant system along with being that much low. This system needs to be right on or the engine will run warmer like you were seeing....There's a air bleeding procedure they may have not done 100% correctly after replacing the thermostat which sits under the big round cylinder tube being the heat exchanger.

Someone stops me on water and says my port exhaust is pumping alot more than my starboard

Click to expand...

That usually tends to be a water flow restriction issue on the raw water side but then again this design engine has done many ghostly phenomenon's in the past and being low on coolant sounds familiar for odd water flow situations like that....I wouldn't be to surprised if that was the overall issue after an thermostat change on this engine.

I start watching the temp guage religiously
it stays a hair above 180 running normal throttle
it jumps to shy under 200 at idle

Click to expand...

Generally with average lake water temps the engine temp shouldn't be much over 179...Maybe 181 on pretty warm lake waters on the gauge side of the system.....The ECM sending unit is usually much more accurate and reads a lower temp vs the gauge when connected to a MPI scan tool device. Usually the scan tool will show about what you were reading with the infrared temperature gun you mentioned this morning vs the gauge.

Is the temp guage on my helm showing my block temp?

Click to expand...

Yes pretty much though the senders are on the crossover tube you just mentioned this morning.
Sensor item number 8 is your gauge temp while sensor 7 is the ECM and Warning Horn for temp....#1 is the crossover tube, http://www.marineengine.com/parts/m...w309999/cooling-system-fresh-water-components

My heat exchanger, manifolds, risers are on raw water correct? I'm not seeing the temp of those on the helm temp gauge correct?

Click to expand...

Correct.....http://www.marineengine.com/parts/m...687083-thru-0w059999/raw-water-cooling-system

If I remove those ends of the heat exchanger... is there anything to be careful about? Do I need to flush and how so. Will I need to watch for air getting in?

Click to expand...

It's generally best to try and order and install new gaskets and bolt seals after each inspection as soon as you can... Part numbers, 25-814878 - O RING, 27-891716 - Gasket -
It's also recommended to use something such as Mercruiser's Quicksilver Perfect Seal or Permatex Aviation Form a Gasket from an auto store and torque bolts to 54-lb-in.

There are bunch of honey comes holes that run down the center of the heat exchanger and they tend to get plugged up with debris at times so its a good idea to inspect them every once in awhile anyways especially if you run in debris type waters like sand, etc. etc.. You shouldn't find any coolant inside the center of the HE, only lake water.....No air issues to be concerned with by removing the center caps too.

Also, when I turn my key to start position, I hear the audible beep... assuming that is testing the alarm? Is the alarm set to the gauge on the helm or to the ecm on the motor? Could there be a problem with the alarm even though its sounding at start?

Click to expand...

While the alarm horn is mounted up under the helm area, it's not part of the actual temp gauge per say....The horn is separated from the gauges and activated by the ECM in this case....The audible beep you hear is a self test system telling you the horn system is working correctly at key up which is good to know since you never heard the horn telling you the engine never truly got to 196+ degrees.

The horn should look like this, https://www.ebay.com/itm/OEM-Factor...6-816492A15-/400635922125?hash=item5d47c306cd

Again air in the coolant system will make the gauge read hotter too on that side of the crossover tube.

So in the dark this morning I checked the coolant level. It took half gallon. I started it up on water hose. It ran 164 at the thermostat with a infrared gun. Helm gauge showed probably 170. I ran it a good 30 mins with captain call on and off if that matters and raising lowering outdrive. And guess what else... its spitting out both tail pipes like normal now.*

Click to expand...

Hope it does all that on the water too...Good luck.

just to check myself...
Is thermostat on port side below the heat exchanger? (Long cylinder deal)?

Click to expand...

Yes in the crossover tube item number 9, http://www.marineengine.com/parts/m...w309999/cooling-system-fresh-water-components

raw water supply coming in from port side underneath? (Read outside temp here)

Click to expand...

After the water flow leaves the impeller housing on the starboard side of the boat/now your left facing the engine inside the boat...The water flows over to the port side of boat/your right side and up into a majority of the engine accessory components....http://www.marineengine.com/parts/m...687083-thru-0w059999/raw-water-cooling-system

Is the long cylinder the heat exchanger? It was 88 on ends... *155 where thermostat comes in.... 135 in middle of cylinder. So it was hottest where thermostat goes in...then decreases to starboard side.

Click to expand...

Yes it is and that all sounds about right temp wise for normal...Hope it stays there for you now.

the "squashed" chamber that runs with length of heat exchanger cylinder???.... it was 154 the length of it....

Click to expand...

Though not important enough for a reply back at this point, Not to sure here...Items that can be considered squashed down would be the pad item number 16 or the 2 seals that hopefully they put 2 news ones in are # 14, http://www.marineengine.com/parts/m.../0m687083-thru-0w059999/closed-cooling-system

Port manifold was 114. Starboard was 109.*

Click to expand...

Sound good enough...Hope it all stayed the same while out on the water for you....Keep close eyes on everything/every trip with your temp gun handy.

​​​​​​​I was told that being a half gallon low shouldn't have given me the symptoms of 182 running 195 idling.*

Click to expand...

Yes it could plus most likely having air in the system would do it too.

The hose coming out of starboard side of heat exchanger/squashed part... was 135 circling back into engine. Is this small hose cooling the block?

Click to expand...

If you can see the following screenshot image, here's the engine water flow for your 496 engine... A = sea water flow and B = Coolant flow.

03playcraft496ho said:

Water test.

temp guage on helm was 180 while running.... infrared gun showed 164.

temp guage on helm 190 while idling... infrared gun showed 170.*

water temp is probably 83 degrees..... so I guess I have to take that into.account for the temp difference than on water hose?*

would you still be concerned at 170? Plus that was on one of those 30 dollar ones ar autozone... think that's accurate? I was measuring right at the thermostat. Where would the temp guage on helm ne measuring at? Should I check into more things since the helm temp guage is so high?

Click to expand...

Didn't see this while texting out all of the above.

Sound like a gauge or sending unit issue....The gauge sending unit is item number 8, http://www.marineengine.com/parts/m...w309999/cooling-system-fresh-water-components

Might want to go through these tests and order a new sending unit to try if possible.....If not try to find another temp gauge and see what happens in order to get the gauge more inline with real time data.
https://www.jamestowndistributors.com/userportal/document.do?docId=842

170 is fine...