Mercruiser 165 Temperature

[ImperialV184]

Hello, know there has been a lot of talk about this and I have been reading many posts. I recently rebuilt a MCM 165. started it the other day with the muffs and noticed that temp sender was not working. Replaced both the gauge and the sender and ran it again. Looks like it is running about 180 per the gauge. Took readings on the manifold and all around the engine and it is consistently around 155-165. I even verified that it is going in heat exchanger at 165 and coming out at 145. Was thinking of putting a manual gauge in the drain port next to the sender to see what it is reading but cant seam to find one and I am worried about the length of the probe. The only other thing I can think of was that I bought the Sierra sender, not the OEM sender, not sure if that matters. When i took it out on the water, the gauge was reading 200, (again IR reader was at 160) did not see any signs of an overheat but not sure what to listen for. appreciate any help.

 

[stonyloam]

You can get a radiator cap gauge like this. https://www.summitracing.com/parts/mrg-2470s/overview/ Normal temp range is 165-200 F for a 470 engine. It is important that the temperature stabilize at all speed ranges, if it continues to creep up after coming up to operating temperature you have a problem.

 

[ImperialV184]

it certainly stabilized at 200 when cruising. it only crept up when I shut off engine and no more coolant flow. as soon as I got underway it went right back down to 200 on the gauge. I like that cap, going to get one. what about the IR readers. If I am firing the reader at the manifold, how accurate are they?

 

[Scott Danforth]

Sounds like the dash gauge or the gauge sender is out of whack