8.1 guardian mode at low rpm

[meadengr]

I have twin inner cooled 8.1 Merc with V-drive on a 2008 Searay 340 Sundancer. The boat goes into guardian mode after it reaches normal temp (163) at idle rpm (670 rpm). After stopping the engine the alarm continues to sound, the alarm sometimes will sound when the engine is not running showing 140 on the temp gauge. Sometimes the system readout says engine overtemp but everything on the engine I check with a temp gun is normal. I changed the temp sensor switch and raw water pump. Problem did not go away. Any suggestions would be greatly appreciated.

 

[dubs283]

I have twin inner cooled 8.1 Merc with V-drive on a 2008 Searay 340 Sundancer. The boat goes into guardian mode after it reaches normal temp (163) at idle rpm (670 rpm). After stopping the engine the alarm continues to sound, the alarm sometimes will sound when the engine is not running showing 140 on the temp gauge. Sometimes the system readout says engine overtemp but everything on the engine I check with a temp gun is normal. I changed the temp sensor switch and raw water pump. Problem did not go away. Any suggestions would be greatly appreciated.

First check for me would be gear lube monitor (if equipped). Second would be diagnostic instrument check for faults.

WAG at this point, given provided info, would be sea water pressure sender fault.

Did you happen to inspect cooling hoses, oil coolers, t stat housing for debris during the impeller r and r?

 

[alldodge]

I changed the temp sensor switch

What's your serial number?
You changed the ECT and not the gauge sensor, correct?

 

[Earl Cordova]

Get a code reader to find out what it is.
There are dozens of possible codes.

On my boat the most common failure is the water pressure sensor.

 

[meadengr]

First check for me would be gear lube monitor (if equipped). Second would be diagnostic instrument check for faults.

WAG at this point, given provided info, would be sea water pressure sender fault.

Did you happen to inspect cooling hoses, oil coolers, t stat housing for debris during the impeller r and r?

Thankyou so much for the reply and I will check those items as you suggested.

 

[meadengr]

What's your serial number?
You changed the ECT and not the gauge sensor, correct?

Thankyou so much for the reply.
Serial number is OW695990
Yes correct I changed temp sensor/ switch not the gauge sensor. The temp gauge reads 162, 163 when warmed up.

 

[alldodge]

Thanks for the SN
Things that cause guardian other then the ones already mentioned
Battery voltage
Engine oil pressure (not the gauge, same as temp has ECM sensor)
CAN circuit fault
Having a V drive so may also be the transmission overheat

 

[meadengr]

Thanks for the SN
Things that cause guardian other then the ones already mentioned
Battery voltage
Engine oil pressure (not the gauge, same as temp has ECM sensor)
CAN circuit fault
Having a V drive so may also be the transmission overheat

thanks for the help. This weekend I will be looking at all the sensors and perhaps swapping with the other engine.