overheating

[Midi0916]

I just bought a 2002 Searay 270SD With 6.2 Mercruiser. It is overheating. I installed a new 160 degree thermostat and sender. I am getting reading between 195 & 225 at idle. Any suggestions?

Thank You

 

[Soulshine]

Determine whether you’re bringing adequate cooling water into the system.

First thing to check is condition or functionality of your raw water pump.

You can disconnect the hose coming from your transom from the thermostat housing, have someone hold it upright and start the engine.

You should see a good 3” plume of water coming out. Hold the hose at the same level as where it was connected.

It could be many things, but this is where to start.

 

[Midi0916]

Determine whether you’re bringing adequate cooling water into the system.

First thing to check is condition or functionality of your raw water pump.

You can disconnect the hose coming from your transom from the thermostat housing, have someone hold it upright and start the engine.

You should see a good 3” plume of water coming out. Hold the hose at the same level as where it was connected.

It could be many things, but this is where to start.

Getting very good pressure

 

[SCORPIO]

Raw water cooled or closed loop system? Is this boat inboard or an I/O?
Your exhaust manifolds and or elbows could be getting filled up with corrosion scale and restricting flow. You could have an exhaust flapper broken and blocking exhaust flow.
We need some more info.

 

[Soulshine]

Yep, that would be next.

Water coming in but no cooling means an obstruction. Look at things in the order of flow.

Next in line after your raw water pump is your power steering oil cooler.

Did you saw trial this boat before buying it? If so, did it over heat then?

 

[CliffA]

a 160* thermostat is the wrong one for that engine....I know you probably installed a lower temp t'stat to get the temp down but that is just a band aid and does not solve the problem...I would suggest putting the correct t'stat back in and continue to troubleshoot the problem...I assume your engine is EFI so it needs to run around 170* to be most efficient....that temp allows the ECM to go into 'closed loop' mode and makes the most out of the inputs from the various sensors to run the engine efficiently....if the engine does not reach that temp you will be wasting full and possibly fouling spark plugs....

good luck....

cliff

 

[thosmann1]

Check your circulation pump on your engine, check your exhaust that plenty of water is coming out. The water coming out of the disconnected raw water hose should be a huge amount of water, is it? Assuming your coolant level is correct, is there coolant circulation in the heat exchanger?
I’m sure you’ll find it, FYI salt starts to crystallize at 200 degrees. It’s important you start running at the correct temp.

Bow Tie

 

[Happy Dayz]

i have extensive knowledge of 6.2 cooling.. was a nightmare on mine with overheating...
found the prior owner servicing left a piece of broken impeller that was wedged in the fuel cooler exchanger inline... best bet is to take the hoses off and literally look through.. i did mine 3 times before i found the piece... once removed, cooled and stays at 165ish

 

[Handsome Transom]

i have extensive knowledge of 6.2 cooling.. was a nightmare on mine with overheating...
found the prior owner servicing left a piece of broken impeller that was wedged in the fuel cooler exchanger inline... best bet is to take the hoses off and literally look through.. i did mine 3 times before i found the piece... once removed, cooled and stays at 165ish

Great advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenance

 

[Midi0916]

Great advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenance

Thank You!!!

 

[Midi0916]

Great advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenance

Thanks

 

[Cast away nick]

Did you ever find the culprit?

 

[Midi0916]

No