Low Operating Temperature?

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   My temp gauge would normally read just below 160 during normal operation but would creep up during long periods of Idling. I replaced the impeller during the off season. 

Since then I have been suspicious that the temp gauge wasn't working because the needle on the gauge wouldn't move above the 100 mark even after long periods of running the engine and idling. Of course I did the bucket/hose/driveway test to ensure the impeller was working, and it definitely is! 

1. I removed the temperature gauge, cleaned all of the contacts and ensured that the connections were good. 

2. I used a test light to test the wire from the gauge and temp sending unit and that was good. 

3. I replaced the temp sending unit with a new marine one from my local marine boat shop. 

4. I went to a vintage speedometer and gauge shop and had them test the gauge and it is working normally. Test included a hotplate with pot of water, and thermometer with the sending unit fully submerged in the water. The gauge accuracy was fairly close to the reading of the thermometer. 

5. I reinstalled the gauge, and used the bucket method in the driveway for a long period of time and the gauge still never went above 100. I collected some water out of the exhaust in a cup and the thermometer read the water temp at 100. 

6. I read through this troubleshooting guide...

Is this a normal operating temperature? 

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Alex47 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: November-11-2010 Location: Tarzana Status: Offline Points: 136	Post Options Post Reply Quote Alex47 Report Post Thanks(0) Quote Reply Topic: Low Operating Temperature? Posted: June-09-2015 at 4:11pm
	My temp gauge would normally read just below 160 during normal operation but would creep up during long periods of Idling. I replaced the impeller during the off season. Since then I have been suspicious that the temp gauge wasn't working because the needle on the gauge wouldn't move above the 100 mark even after long periods of running the engine and idling. Of course I did the bucket/hose/driveway test to ensure the impeller was working, and it definitely is! 1. I removed the temperature gauge, cleaned all of the contacts and ensured that the connections were good. 2. I used a test light to test the wire from the gauge and temp sending unit and that was good. 3. I replaced the temp sending unit with a new marine one from my local marine boat shop. 4. I went to a vintage speedometer and gauge shop and had them test the gauge and it is working normally. Test included a hotplate with pot of water, and thermometer with the sending unit fully submerged in the water. The gauge accuracy was fairly close to the reading of the thermometer. 5. I reinstalled the gauge, and used the bucket method in the driveway for a long period of time and the gauge still never went above 100. I collected some water out of the exhaust in a cup and the thermometer read the water temp at 100. 6. I read through this troubleshooting guide... Is this a normal operating temperature?
	1977 Ski Tique

D&C1988 Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: February-16-2015 Location: TableRock Lake Status: Offline Points: 67	Post Options Post Reply Quote D&C1988 Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 4:55pm
	I no mechanic by any means but just dealt with this myself on the maintenance update on the 88 I bought over the winter. There was no thermostat in it and with a new impeller it never went over about 125. Just a guess.

Gary S Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096	Post Options Post Reply Quote Gary S Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 6:59pm
	Could be stuck open too,you'll just have to pull off the housing and look.
	69 Mustang HM SS 95 Nautique Super Sport

8122pbrainard Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045	Post Options Post Reply Quote 8122pbrainard Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 8:39pm
	Alex, Check your voltage to the gauge. You should be getting 12 not running and higher with the engine running. Was any type of thread sealant used on the sender? There should be none. It will interfere with the ground path to the engine block. With a VOM, between the threaded body of the snder and the block, you should get 0 Ohms. Get rid of the test light! A cheap VOM is around $20 and will do most jobs in the boat, car and house.
	54 Atom 77 Tique 64 X55 Dunphy Keep it original, Pete <

Alex47 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: November-11-2010 Location: Tarzana Status: Offline Points: 136	Post Options Post Reply Quote Alex47 Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 10:06pm
	Pete, Yes, the sending unit came with sealant on the bottom half of the threads. Should I remove the sealant on the sender and retest the bucket method? I'm under the impression that the water isn't getting warm enough to make the temp gauge read above 100.
	1977 Ski Tique

Alex47 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: November-11-2010 Location: Tarzana Status: Offline Points: 136	Post Options Post Reply Quote Alex47 Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 11:51pm
	The multimeter read 10.4v at the temp gauge with the ignition in the "on" position, and increased above 12v with the engine started. I tested the gauge and sending unit while installed in the boat by removing the sending unit, attaching alligator clips and submerging it in hot water in a mug with a thermometer. Again, the temperature on the thermometer matched the temp reading on the gauge.
	1977 Ski Tique

8122pbrainard Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045	Post Options Post Reply Quote 8122pbrainard Report Post Thanks(0) Quote Reply Posted: June-09-2015 at 11:58pm
	Alex, IR thermometers are cheap these days. Get or borrow one and shoot the temp of the block as close to the sender as possible. You'll need to let the engine run for awhile since the water gets warmer faster. It will not be an exact temp but should be close. It was mentioned about a T stat stuck open. Have you checked it?
	54 Atom 77 Tique 64 X55 Dunphy Keep it original, Pete <

Alex47 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: November-11-2010 Location: Tarzana Status: Offline Points: 136	Post Options Post Reply Quote Alex47 Report Post Thanks(0) Quote Reply Posted: June-10-2015 at 5:22pm
	There was no thermostat! I just installed a 143 degree thermostat. Waiting for the gasket sealant to dry, then i will bucket test tomorrow!
	1977 Ski Tique

Gary S Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096	Post Options Post Reply Quote Gary S Report Post Thanks(0) Quote Reply Posted: June-10-2015 at 6:19pm
	Great Alex. Keep a eye on it sometimes people remove it to keep it cool because of a blockage.
	69 Mustang HM SS 95 Nautique Super Sport

Alex47 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: November-11-2010 Location: Tarzana Status: Offline Points: 136	Post Options Post Reply Quote Alex47 Report Post Thanks(0) Quote Reply Posted: June-12-2015 at 2:26pm
	Looks like we solved the problem! The bucket test resulted in the engine temp at a steady 160 during idle, and dropping to 140 when I advance the throttle. Thanks for your help!
	1977 Ski Tique

D&C1988 Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: February-16-2015 Location: TableRock Lake Status: Offline Points: 67	Post Options Post Reply Quote D&C1988 Report Post Thanks(0) Quote Reply Posted: June-12-2015 at 4:03pm
	BINGO !!! I got one.... Happy boating.

Low Operating Temperature?

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