Port Side Cylinder Head Temperature Sensor Issue 02 utopia 185 240 efi

[6MISFITZ]

After we bought our boat last year, there were some poor running issues.
From reading this blog and its stickys, one of the first things I checked was the Port Side Cylinder Head Temperature Sensor. Its ohms reading given the outside air temperature showed it was way off - re Mercury ohms chart page 2A-18 Mercury Manual # 90-884822

My 02 Utopia engine's # is OE397584.

I took my serial # to my dealer and ordered a complete set of spark plugs, 2 plug wires, 2 fuel filters and port side cylinder head temperature sensor 13536A14 (the part number they gave me).

After the install of above parts, the boat started first try, idled smoothly and full power for pulling a skier out of the water or full speed was always ready.

Having issues with the boat on power last month, tested ohms reading on same sensor and it was way off agian. Shows 950 ohms at room temp which according to chart is around 190 degrees Fahrenheit.

Ordered a new sensor again, tested it at the dealer, showed 8000 ohms or room temp of around 78 degrees.

Tested it again Sunday while trying to get cylinder compression #s and it showed 950 ohms.

Took it to dealer and tech opens different manual says my ohms 950 reading is correct for room temp. The fact that my sensor showed 8000 when I bought it two weeks ago does not matter. Their manual says it should be just under 1000 ohms at 70F.

Do I have the correct part number for the port side temp sensor?
What is the latest / newest mercury manual with the correct ohms chart please?

Mike

 

[Dr Honda]

You have an early (2001) 240 EFI engine. So yes... the port side temp sender # is 13536A14. AND... it should read around 1k ohms, at room temp. (72 F)

Are you checking the sender disconnected?

 

[Dr Honda]

I think I see the issue....


You should be looking at manual 90-877837. The manual you listed is for the 2001-1/2 and newer engines. They have a totally different EFI system.


The newer 240 EFI starts at S/N OE4064000

 

[6MISFITZ]

Checking the sensor both on (2 male terminals) and off the engine.
Both times, sensor starts reading 990 - 1000 and then ohms drops down to 922 - 930

Mike.

 

[6MISFITZ]

Sorry not enough info in my above reply.

Have read that a noticeable drop in low speed performance and visible smoke in exhaust after engine heats up is a good reason to test this particular sensor.

4 wire port head sensor
same 2 male terminals tested each time.
1 Female terminal
1 Ground ring

Mike.

 

[6MISFITZ]

Tag on new sensor says up to 1000 - 10,000 ohms so I was concerned after seeing readings drop below 1000 ohms.

M.

 

[Dr Honda]

Sounds like your sender is OK to me.

Room temp 950~1k. running temp should be around 400 ohms. Freezing is 2.8k~3k ohms.

 

[6MISFITZ]

Thank you, for the confirmation.

Mike.