2008 4.3 ltr mercruiser overheating alarm

[Larry Baloun]

So this is the 3rd season I have tried to resolve this problem. My boat runs 170-175 degrees. When it hits 175 the alarm beeps intermittently. I usually rev it in neutral until the heat drops. I have replaced the water impeller, the heat sensor and the thermostat (160 degree). I have also confirmed with a temperature gun that the gauge reading is the same as the areas near the thermostat. The fuel mix setting on the carb has been adjusted to ensure it is not too rich or lean.
What else can be done? What part should be replaced to have the alarm sound at 190-200 instead of 175?

 

[dubs283]

What part should be replaced to have the alarm sound at 190-200 instead of 175?

the over temp switch. i'm not sure what the spec temp is for activating the switch, though 175 does seem low

 

[Scott06]

So this is the 3rd season I have tried to resolve this problem. My boat runs 170-175 degrees. When it hits 175 the alarm beeps intermittently. I usually rev it in neutral until the heat drops. I have replaced the water impeller, the heat sensor and the thermostat (160 degree). I have also confirmed with a temperature gun that the gauge reading is the same as the areas near the thermostat. The fuel mix setting on the carb has been adjusted to ensure it is not too rich or lean.
What else can be done? What part should be replaced to have the alarm sound at 190-200 instead of 175?

did you replace the temp switch that triggers the alarm? did you check your exhaust manifolds and elbows for clogging? This can restrict water flow mostly in salt or brackish water use

 

[Larry Baloun]

the over temp switch. i'm not sure what the spec temp is for activating the switch, though 175 does seem low

Where is the over temp switch?

 

[Larry Baloun]

did you replace the temp switch that triggers the alarm? did you check your exhaust manifolds and elbows for clogging? This can restrict water flow mostly in salt or brackish water use

I believe what I replaced was a sensor not a switch ...where is the switch?
How do you check the manifolds/elbows for clogging?

 

[Fun Times]

I believe what I replaced was a sensor not a switch ...where is the switch?
How do you check the manifolds/elbows for clogging?

Item number 6 would be the proper "sensor" that reads/sounds the temperature over heat alarm, https://www.mercruiserparts.com/bam/subassembly/31493/12833/170

Should have had Yellow and Black wires going to it.

You may be experiencing an phantom alarm which if everything else seems exhausted, try following the info found within the following link,

4.3L TKS intermittent engine alarm

Hey everyone. Need some help troubleshooting an intermittent but worsening issue. This is going to bed long-winded, but bear with me. Here's some back story: I have a 2007 4.3L TKS engine w/ Alpha One Gen II outdrive on a 2007 Bryant 210. I've owned it since 2016, I'm the 3rd owner, when I...

forums.iboats.com

 

[dubs283]

I believe what I replaced was a sensor not a switch ...where is the switch?
How do you check the manifolds/elbows for clogging?

switch is usually located near or in the t stat housing

need to pull the risers off the manifolds to check for blockage

 

[Larry Baloun]

switch is usually located near or in the t stat housing

need to pull the risers off the manifolds to check for blockage

Is there a how to somewhere on removing the risers (I am not exactly sure which parts to remove).

 

[Larry Baloun]

Item number 6 would be the proper "sensor" that reads/sounds the temperature over here alarm, https://www.mercruiserparts.com/bam/subassembly/31493/12833/170

Should have had Yellow and Black wires going to it.

You may be experiencing an phantom alarm which if everything else seems exhausted, try following the info found within the following link,

4.3L TKS intermittent engine alarm

Hey everyone. Need some help troubleshooting an intermittent but worsening issue. This is going to bed long-winded, but bear with me. Here's some back story: I have a 2007 4.3L TKS engine w/ Alpha One Gen II outdrive on a 2007 Bryant 210. I've owned it since 2016, I'm the 3rd owner, when I...

forums.iboats.com

Wow! This is amazing it sounds just like my issue. What a wealth of info. I sure hope the ICM connect/disconnect works. However, I take the battery out for the winter so I won't get too hopeful.

 

[Larry Baloun]

Item number 6 would be the proper "sensor" that reads/sounds the temperature over here alarm, https://www.mercruiserparts.com/bam/subassembly/31493/12833/170

Should have had Yellow and Black wires going to it.

You may be experiencing an phantom alarm which if everything else seems exhausted, try following the info found within the following link,

4.3L TKS intermittent engine alarm

Hey everyone. Need some help troubleshooting an intermittent but worsening issue. This is going to bed long-winded, but bear with me. Here's some back story: I have a 2007 4.3L TKS engine w/ Alpha One Gen II outdrive on a 2007 Bryant 210. I've owned it since 2016, I'm the 3rd owner, when I...

forums.iboats.com

One other thought, you sent me a parts diagram and said "part #6 was the sensor. I have replaced part 6. Should I also try replacing part dwg. # 3 ? What does that part do?

 

[Fun Times]

Part # 3 operates the temp gauge at the dash only.

 

[Larry Baloun]

Part # 3 operates the temp gauge at the dash only.

Isn't the alarm part of the gauge?

 

[Larry Baloun]

Part # 3 operates the temp gauge at the dash only.

So two days ago I detached and reattached the wiring to the ICM ...there has been no beep for 2 days - I can't believe it! 3 years of trying to replace things and diagnose the problem and a simple disconnect/reconnect fixes it. Thank you so much for your help!!!

 

[Fun Times]

So two days ago I detached and reattached the wiring to the ICM ...there has been no beep for 2 days - I can't believe it! 3 years of trying to replace things and diagnose the problem and a simple disconnect/reconnect fixes it. Thank you so much for your help!!!

You're welcome...(sort of an iboats forums exclusive with this one )...Please come back and let us know if or when it comes back up like this....Maybe keep track of engine hours, etc...Thanks and good luck.

Sharing a recent private message regarding the same subject,

Jun 16, 2021
Good evening!

I just wanted to tell you thank you for the insight regarding the phantom alarm issues on this post: https://forums.iboats.com/threads/4-3l-tks-intermittent-engine-alarm.733967/

I unplugged the module, applied some dialectic grease, reconnected and then viola! No more beep!

thank you for spreading your knowledge!

Chris