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MerCruiser 4.3 temperature alarm

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AA2052

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I recently purchased a 2006 Trophy 2052 equipped with a MerCruiser 4.3L engine (Thunderbolt ignition). I was told that the engine had been refurbished about three years ago, including the installation of new exhaust manifolds and other components.

Before launching the boat, I took it to a mechanic for a complete service. According to him, he replaced the engine oil, oil filter, fuel filter, impeller, thermostat, and idler pulley, among other routine maintenance items.

The first time I used the boat, the temperature alarm sounded after the engine had been idling for approximately 45 minutes. At that point, the temperature gauge had risen to about three-quarters of the way up the scale.

When I contacted the mechanic, he told me that I should not leave the engine idling for that long. However, I am concerned that there may still be an underlying cooling-system issue. I also noticed that the hoses on the left side of the thermostat housing become warm, while the hoses on the right side remain cool.

Does this indicate a possible problem with the cooling system, and what could be causing it?
 
You can idle for days with NO issues. The ""Mechanic"" is wrong

So the Mechanic is 100% responsible for the issue if it is related to any of his work.

Ask him, Then why can someone go fishing-trolling at idle speed for hours with ZERO ISSUES????

If he cannot answer that correctly, then find another mechanic
 
At that point, the temperature gauge had risen to about three-quarters of the way up the scale.
Click to expand...
3/4 up may not be hot, what was the temp reading in degrees

How do you know it was the Temp alarm?

There are other things that can cause a solid alarm to sound off, low drive lube, low oil pressure
 
My gauge doesn't clarify degrees, only quarters, im assuming 175 degrees.

I touched the hoses on the left of the thermostat and they were warm, the ones on the right were cold. That's why i assumed it's the temp.
 
175 wouldn't be a overheat, and one side being warm and other cool is normal. The cool side is raw water which is ready to go into the block when the thermostat opens and also the water that goes to the exhaust.

Check the drive lube reservoir and see how much lube is in it. The bottle will have a full level marking on the bottle.

Look at the oil pressure to see if it's going low
 
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