4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

[dtescher]

My boat has been running cold according to the temp gauge. I pulled the brand new sensor(sensor ohm tests are in the right range). Placed it in a cup of boiling hot water. Alligator clipped it to the sensor post on the gauge and grounded the threads. Couldn't get it above 100 degrees. Is this a bad gauge or something else?

 

[Don S]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Pull the thermostat housing, remove the stat, and check the housing. There is a bypass hole in it that is plugged up with rust or an old piece of impeller or something.

 

[dtescher]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Thanks Don S. Just to clarify. I pulled the sensor out of the motor and tested it directly on the gauge separate from the motor. So, if the the thermostat is not involved how would it be a factor?

 

[Don S]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

I'm not talking about the sender or the thermostat. I am talking about a bypass hole drilled in the thermostat housing.

 

[dtescher]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

OK. I'll check that. But, I'm confused. If I tested the sensor directly on the gauge independent of the thermostat or motor with boiling hot water. How is it that I can't get a reading above 100 degrees on the temp gauge?

 

[Don S]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Use the boiling water test, but use an ohm meter. What do you get in cold water and 200? water? That is how you check the sender.

 

[dtescher]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Cold water 700-900 ohms, Hot water 90-70ohms.

 

[Don S]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Water Temperature --- Ohms Reading
140? F (60? C)--------- 121-147
194? F (90? C)---------- 47-55
212? F (100? C)--------- 36-41

 

[dtescher]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Update below!!!

 

[dtescher]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Update! Don S. you are a genius! So, I went back and took the thermostat housing off again and looked for blockage. I didn't notice this before. But I saw what you were talking about, the bypass port. Didn't realize it's so small. On closer inspection I noticed that the port was clogged with impeller rubber. And I mean jam packed. Took a while and some dental tools to clear it. But once I did I re-assembled it and ran it on muffs. Just like that the temp gauge started working and ten minutes later it was at 175 degrees. Thank you so much.

 

[JoLin]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

So, dumb question- if the bypass is blocked, is the engine running cold, or is the blockage interfering with the gauge reading? I have the same problem on my twins- temp gauges both read about 125 with the motors warmed up.

(I feel like I should know this one, but I'm having a senior morning...)

 

[Don S]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Yes, the engine is running cold. With the bypass hole plugged up, the pressure from the raw water pump forces the thermostat open and the engine never gets a chance to warm up.

 

[JoLin]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Gracias!

 

[MasterGoa]

Re: 4.3 GL PLKD Temp Gauge Not Getting Above 100 Degrees

Thanks again Don, from where ever you are now