Overheating with closed cooling system???

tony1b2000

Active Member
Oct 10, 2007
243
Salem MA
Boat Info
Carver C37
Engines
Mercury Diesel 4.2 TDI, inboards
Getting an occasional "overtemp" fault on smartcraft. Port motor Goes into guardian mode.
I have a closed system. Just changed the raw water impeller today. The old one looked fine.
Not sure of next steps. Mechanics are booked out up here.

Any suggestions?
 
Heat exchanger could be clogged.

Thermostat stuck closed

Coolant level low.
 
IO's or inboards?
Trace the flow of water from the source to the heat exchanger. If it passes through an oil cooler or sea strainer, clean those first. Next, inspect the heat exchanger tubes and flush out with fresh water. It's possible that some debris is clogging the exchanger or oil cooler/sea strainer.
If all that checks out, check the exhaust elbows and manifolds for scale build up and restriction.
A stuck thermostat could also cause heating, as could low coolant in the exchanger tank. BTW, be sure the radiator cap on the exchanger is tight and not leaking off pressure.
 
I have i/o's. The engine package came with Seacore. Suppose to be additional protection.
The boat is a 2010. How long is a heat exchanger / and elbows good for on a closed cooling system? Called merc. They suggested having a mecanic hook up the G3 software. Anyone familiar with that? Worth buying?
 
What is the fault code on your Smartcraft? Also, as asked above, what is your H2O water PSI? Need the readings at idle, 1200 rpms and 3200 rpms. (Record both motors) Does it overheat all the time, slow rpm as well as high?This is actually quite easy to track down. Shouldn't need the software, it is just a matter of finding the restriction, either before the pump or after.
 
Korkie, I decided to take the boat out today to compare the two engines as you noted via vessel view. Port temp has been coming as as the problem. When I ran today, The port pressure is better then the starboard. probably cause I just changed the impeller. For one reason or another, I got multiple alarms. I think the most important being " Engine sensor" Water pressure sensor not working properly ( see attached photos )!!! Eng temp readings looked fine.


Now I just have to figure where this part is located!!!

Thanks All
 

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I had to replace both on water pressure sensors on my new to me boat in the first 4 months. I now keep a spare, but will probably get a second for a longer trip, or just replace them. I have v drives, so I think mine is located in a different location.
 
I assume the alarm is for the raw water pressure. That sensor is likely on your power steering cooler at the rear of the motor on the top. Easy to see and get to.
 
Awesome, will take a look tomorrow!

Odd there are 2 presures indicated on vessel view. the second and 4th in the attached picture. Does anyone know if one for circ pump (closed cooling and one for the raw water ? And which is which?

Thanks
Image-2.jpg
 
I just launched and experienced what would have been an overheat situation on my port engine. As part of my normal spring commissioning I idle the engines after launch and watch water pressure and engine temps on both engines. Sure enough my port had poor water pressure and rising temps. Pressure would increase with throttle but not equal to the starboard. Starboard manifolds were cold to the touch but port were much warmer for the same period of time.

Quick inspection should what I would consider too much deflection on my serpentine belt so I am hoping the pump is just slipping and not moving enough water. Only problem is my tensioner bolt must have been replaced in the past and its short and all the way in so no way to add more tension. Gonna try to fix that next.

Just mentioning this since it give me a chance to vent and gives you another inspection point for troubleshooting.

-Kevin
 
Top pressure is oil pressure, lower is water pressure.
I do not believe either of those water pressures, or you have a restriction in both engines after the raw water pump.
 
Not an expert on outdrives, but two things come to mind.

There have been cases where the water pickup hose coming from the outdrive to the belt driven water pump on the engine have become restricted with corrosion. The solution chosen by many has been to install thru-hull fittings directly through the hull bottom to feed the water pump and bypass the drive's water supply.

The other issue with these engines can be the water pump itself. Even though a new impeller was installed, the pump's housing is soft brass which can become scored enough at the front and back end to reduce the ability to provide adequate water pressure - especially at higher speeds. Solutions range from replacing the pump with another OEM, replacing the pump with a stainless aftermarket alternative, or adding an aftermarket kit which includes stainless end plates that are installed into the OEM pump and a matching impeller that is reduced in length to account for the width of the end plate.

If you suspect the pump, you can check out this site for the aftermarket kit... http://www.marine-496pump.com/
(no affiliation)
 
$145 later and 5 minutes to change! Water pressure sensor was it.
Thanks for all the help!
20180519_075417.jpg
 
Did you replace the sensor on one or both motors?

Post some water pressure readings from your next trip. As stated earlier, those pressures (35-40psi) seem very high.
 
Purchased a spare to keep on board! This sensor going bad put me into guardian mode. Not something I want on a long trip away from home.

PSI at idle: 6
PSI at 1200 RPM: 17
PSI at 3600 RPM: 40

Not sure how truly accurate the sensor is. The main thing I was concerned with is maintaining proper engine operating temperature.
 
Hi guys, I know this post is a couple of years old, but I wanted to see what you guys thought about this water pressure:

could that mean I have a problem with one of my engine? Or a sensor?

I have Merc 350 Mag with Bravo 3 sea ore Outdrives and my smartcraft gives me some overheating errors as well. The temp on the screen shows 160-170, and laser temp reader shows no overheating when I open the engine bay.
 

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Always could be a sensor, you could possibly swap the sensor and see if the "problem" follows the sensor.
High pressure indicate a restriction after the raw water pump.
Low pressure indicates a restriction before the water pump, or worn out pump.
Do you have thru hull raw water pickups? or thru the out drive?
try this good discussion...
http://clubsearay.com/index.php?threads/bravoitis-or-deeper-overheating-issue.100042/

Bravoitis is an issue with the fittings in the transom corroding and clogging restricting flow.
iu

iu
 
Thank you for your response!
I not sure how to check where the raw water pickups is or how to find out...

I just purchased the boat and the outdrives were serviced, so I'm not sure, but it's probable that the fittings have been checked.

I'm going to order a couple of the sensors so I can test that as well.
I will update the thread when I replace them.

What should be the pressure at these RPM, speeds.
 

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