Engine Temp Way Below Normal

[RichG]

Hoping to get some advice. We're on vacation on Castlerock Lake in Wisconsin with the boat. Its the 4th largest lake in Wisconsin but its relatively shallow with a sand bottom (up to 36 ft depth max). Well, despite my efforts which included ordering and memorizing a lake map with depths, using the boat gps to navigate around shallow spots and talking to locals about any underwater hazards..... I managed to ground the boat on an unmarked sand bar. I hoped to get off the bar by trimming up the engine and slowly trying to coax her off - but that didnt work. So everyone was in the water pushing her back to normal depths. All was well and good. Except 5 minutes later I noticed the engine temp dropping to the bottom of the gauge and the "check engine" alarm sounding every 1 minute. I let the engine idle for a while to see if the temp would come back up. No dice. I called my marina back home and they thought it could be a bad thermocouple sending bad temp readings or sand getting into the intake and wedging the thermostat open. After much debate I decided to try heading back to my vacation marina 20 minutes away. On the way back, the temp would rise to normal 170 degrees, then fall back to the bottom of the gauge. The last 5 minutes of the trip the gauge came up and stayed steady at 170, but the alarm still beeping every minute. After golfing and dinner, I went back to the boat and let it idle for 10 minutes at the marina. Temp never came up off of gauge bottom and alarm soulnded every minute. Any suggestions what this could be? and is it harmful to operate the engine at low temperatures? ( I assume it is). Thanks for any advice you can give. Rich

 

[kaz911]

It sounds like a temperature gauge problem. How fast did the temperature change? Within minutes? Cooling the engine to very low temperatures does not happen in 5 minutes.

EDIT : Do you not have SmartCraft? I hate "just engine beep alarms"

 

[RichG]

Great point. The engine temp didnt nose dive to zero, but slowly descended from normal to gauge bottom within 5-8 minutes while running. Even with wide open thermostat you wouldnt think it would cool down that much. So maybe the sand experience and timing of the temperature issue is a coincidence. Something to think about.

 

[kaz911]

hmm - just looked at a picture of the 383 - slightly different to what I'm used too - so I will not comment on what to do. apart from be careful! - and don't run the engine before you find out if it is the sensor or thermostat.

 

[dev6315]

I have an older engine but I had a similar problem the beginning of this season. After making sure the gauge was working as it should, I replaced the sender on the thermostat housing and it worked like a charm. $25.00 fix and about 10 mins.

 

[northern]

You might want to purchase a temperature gun ($30 to $70) at any auto store. Read and record temperatures at various place on the engine and exhaust system when cold, warming up and running, cooling down and at various running speeds. It may tell you if it is a gaude, sending unit, thermosat, plugged water way. Do not ware loose cloths if you use the gun when the boat is running and make sure some one is watching you so they can shut down boat if there is a problem. Safety glasses are a good idea also.

 

[RichG]

Quick update. After talking to local marine store, I took out the thermostat and cleaned it up. There were a few pepples around the base of the thermostat and housing. Just to rule out the thermostat I replaced it. Upon starting, the engine came up to temp - but the smartcraft "check engine" alarm still beeps every minute. All gauges read normal now - so I'm planning to go out on the boat this afternoon, keep a sharp eye on the gauges and stay within a mile of the marina. Need to determine why the check-engine keeps beeping. Rich

 

[rcknecht]

Your flow through the engine might be restricted causing the alarm to go off for a low Raw Water flow rate. I would probably change the water pump in the out drive...