Mercury 115 Hot Cylinder

[hermannm]

Hi I have a Mercury 115 that the top cylinder is getting significantly hotter than the other 3. The top one is hot but can still be held with your hand. The rest are lukewarm. Any ideas?

 

[Faztbullet]

When was impeller last serviced and t-stat checked???

 

[hermannm]

I just replaced the thermostat and recently checked the impeller. There is a steady stream of water out the tell tale.

I also replaced the head gasket and exhaust gaskets to fix the water that was entering the cylinders.

 

[Faztbullet]

Whats your model number as no head gasket on a 4 cylinder....

 

[hermannm]

It's a 1992 mercury 115. Its the gasket for the front of the motor that goes over the spark plug holes. Not really a head gasket I agree

 

[Faztbullet]

Replace impeller every 2 years no matte how well it pees....

 

[hermannm]

How warm should the water be coming from the tell tale hole? The water is only slightly warmer than the lake water. Also the other 3 cylinders are cool to the touch, about room temperature. The top cylinder is hot, but can hold my hand on it. Is this normal or any ideas on what may be causing the issue?

 

[Faztbullet]

Your pee comes off the exhaust plate and its a indicator and tells you nothing about engine cooling. If impeller is weak even though you think its peeing good its possible the block is not fully filling at idle.Thus top cylinder warmer.....has killed many a TOP motor

 

[hermannm]

Thanks Faztbullet, I will replace the waterpump impeller today. What temp should all the cylinders be? Should they be cool to the touch? The thermostat is 120 degrees. I appreciate all your help!

 

[hermannm]

Doh. Its a 2+2. No wonder the top two cylinders were getting hot.

 

[QBhoy]

Doh. Its a 2+2. No wonder the top two cylinders were getting hot.

What does this mean ? Thanks.

 

[Faztbullet]

Nothing really....water still circulaters thru block. A 2+2 only runs on the top 2 cylinders up to 1800 rpm

 

[QBhoy]

Nothing really....water still circulaters thru block. A 2+2 only runs on the top 2 cylinders up to 1800 rpm

Thought as much, haha.