Yanmar 4jh4 hte

[rector67]

I have a 2012 Yanmar 110 hp on power catamaran and the temperature gauge is steady at 175 until I put more then 1000 rpm . Then it starts jumping and fluttering from 180 to 225. Randomly sets back to 175 then fluters again. Checked anti freeze good, checked raw water flowing, strainer clean. I back washed the strainer out to intake with fresh water hose, seemed to help but not at higher rpm. Any suggestions? I also checked wiring from thermostat seemed good connection

[Shrew]

I had a car that used to do something similar. Temp would rise, then fall, then rise again. Kind of bounce around. It turned out I had an air pocket in the AF. Bleed the system and it was fine.

On the other hand I had a boat once, that every time the 12v fridge cycled on, the engine temp gauge rose about 10-15 degree's. I attribute this to an odd voltage drop issue. Sold the boat, but never solved that mystery.

In general with heat issues, if you've narrowed down the water pump and raw water flow, you might have constriction in the heat exchanger.

[rector67]

Thanks

[GreenWave]

Your problem could be a simple electrical connection. When you say flutter around how fast are these changes? Seconds or minutes? If former then likely electrical. Spray the harness and clean the contact on your panel. Also check your sender connections.

[rector67]

Seconds on the flutter. Cleaned connectors on engine

[rector67]

The harness?

[rector67]

Not impeller?

[GreenWave]

If it is fluttering very quickly then it is very likely either a connection or the sender itself.

[rector67]

Thanks. Tried to loosen sender to clean but could move it

[rector67]

Thanks for your help

[GreenWave]

Originally Posted by rector67

Thanks. Tried to loosen sender to clean but could move it

Do you mean you couldn’t move it? I had issues with mine and pulled the spade connectors off, cleaned them and sprayed corrosionX on them. Problem solved.
If you can do this if may help. If that doesn’t work then you should try a new sender.

[rector67]

Pulled off and cleaned both ends still have problem

[GreenWave]

Do you have an infrared temp gun? Wondering if you can validate the temps via other means?

[CarlF]

Replace the sender. Cheap and a common failure.

Check the wire and plug for any signs of corrosion. Use a good contact cleaner spray. Consider making up a new wire.

Use a handheld infrared thermometer aimed right at the sender. Look for any “flutter” there.

Finally, suspect the gauge. Also a common failure.

[rector67]

Thanks. I tightened belt again so we will see what the day brings