Mercruiser 6.2 engine cooling problem

Good morning


Please let me know if you can help mi with the Mercruiser 6.2 engine cooling.


Regal 26 Express yacht, 2017, Mercruiser 6.2 engine. 230 mg


I was sailed the yacht in 2019 in the Adriatic Sea. There was no problem.


I was not saild in 2020. I made yacht service. I drained water and filled glycol filling.


The pump implerer was replaced. After replacing there was some a problem with the pump drawing the water and the engine was overheated on the land.


In 2021, the engine worked properly for 10 minutes after I put the boat to the water.


Leaving the port after 10 minutes, making a 180-degree, 10kn turn, I heard bubbling from behind under the aft platform and noticed white / gray smoke from under the platform. I also heard a squeak, an engine alarm and the lever became useless. max speed up to 7 kn.


I turned it off and nothing has changed.


I turned off again ant the problem was canceled, it was possible to sail.


However, every time after relapse, the problem appeared. The temperature jumps towards 100 degrees Celsius and the water pressure drops below 10 kPa.


One day I could siled without faults


Currently, the problem arises when swimming straight ahead.


After a few minutes of swimming, the temperature jumps to 100 ° C and the water pressure drops below 10 kPa.


The holes that suck the water are clean. Nothing wrapped around the bolt.


In my opinion, there is a problem with water intake for cooling. Perhaps the elements are salted by the waters of the Adriatic Sea (although the yacht was sailing normally for one day, no faults). The second one may be a defective Implerer. Pipes at the zip line are clean, undamaged.


Please guide me to the problem, where to check defects.


Currently, the yacht on the land

The pump implerer was replaced. After replacing there was some a problem with the pump drawing the water and the engine was overheated on the land.

Click to expand...

The impeller was probably installed backwards...blades are not sucking water because some if not all of them are installed backwards.

Ok. I will check it. But how can you explain the it worked for one day withoute any problem with cooling ?

my mechanic said that it does not matter how the impeller is install because the blades will turn. is it true ?

Your mechanic is correct, the impeller will right itself....

Change the impeller.... Hard to run this on a hose.....

Thank you.

I will try.
Is it possible the brend new impeller can be wrong.

What do you think about crab or shell inside or other ser Animal.

The problem could be that air is entering the system between the water intake and the pump. Tighten all connections (hose clamps) between hoses and fittings.

Do you have a sea strainer? Does the strainer have a removeable lid with a gasket? If so, the gasket may be leaking air into the system.

Just a small air leak can disrupt the vacuum needed to pull water into the pump.

Thanks for your conception. Your are also right.
I do not have sea strainer. Here you have the photo the part of engine. There, you can find som holes.

For this time a have som conception
1. to change impeller
2. to tight all connections between hoses and fittings
3. to clean the crabs, shells etc form salt Adriatic sea (I did not s
4. seal risers (because the exhaust fumes can push water out of the cooling system)


that is crazy. My boat is dead

Here you can find the bubbles I wrote about on the beginig

As DJR wrote it is possible that exhaust gas disrupts the water. So exhaust gas back to the engine with the water and there is less of water so the temperature rise. So I have to check the exhaust pipe?

Thank you for help. Everything is ok.
The problem was with water pump

The end