Airplane trick...swap to the other side and see if the problem follows.

 

Absolutely! Both of mine went bad within a year of each other.

 

Thanks. Never even thought about that "airplane trick". I will do the switch this coming weekend.

 

This is a good guide to troubleshoot water temp gauge.


http://www.jamestowndistributors.co...l/document.do?docId=842&title=Troubleshooting+Teleflex+Water+Temperature+Gauges

Temperature systems used on boats and other vehicles give a general indication of the temperature in which the sender is operating. We use the term "general" as the system can vary to a maximum 15 degrees from actual temperature.



The gauge itself is accurate to within about 5 degrees at the mid-scale position. The sender is accurate to within 10 degrees at 200 degrees (as are competitive units). The sender tolerances widen as temperatures become higher or lower than 200 degrees. Although sender/gauge tolerances rarely run to the maximums (at the same time), the system can possibly indicate up to 15 degrees difference from actual temperature at 200 degrees. These specifications are developed at a system voltage of 14 volts. The sender is also susceptible to "self heating" when electrical current passes through the sender. The self heating causes the sender to become warmer than the actual temperature of the fluid (the gauge is compensated for this effect at 14 volts). If the system voltage is varied to 13 or 15 volts the gauge may read 5 to 6 degrees higher also.
In a few cases it is necessary to put a temperature sender and a temperature switch (to operate a light or buzzer) in the only engine opening. In this case a "tee" is used. However, when the sender (or switch) is moved away from the water flow, the water around the sender bulb tends to run cooler. The gauge will also show a cooler reading than the actual water temperature inside the engine. Use of "extenders" or "tees" is generally not recommended.



Water Temperature System (Inboards & Stern Drives)

1. To test gauge, voltage from "I" to "G" terminals must be 10-16 VDC. No wire on "S" terminal. Gauge pointer should rest below 120. Next, connect the "S" terminal to the "G" terminal (leave "I" and "G" terminals connected). The gauge pointer should rest above 240.
2. The resistance of the sender can be measured to determine the sender's correct operation. Remove wire to gauge. Connect an ohmmeter to terminal of sender and to engine block. Approximate values are: 75 (room temperature) = 600 to 800 ohms; 212 degrees = 55 ohms. (These are single station values- twin station values would be 1/2 these numbers).
3. If sender is shorted (0 ohms) gauge will read above 240F.
4. If sender has infinite resistance (Open) gauge will read below 120F.
5. If the gauge reads lower than expected, was sealer used on the sender threads? (See illustration.)
6. The accuracy of the system (gauge, sender, voltage range) can vary as much as 16 degrees at 180F.
7. Use of pipe extenders to plumb both a sender and temperature switch (for horn or warning light) from one port is not recommended. The amount of weight extended on the fitting of a vibrating engine could cause fatigue-related breakage. Also, the sender is removed from water flow inside the engine and will probably read cooler.
8. Teleflex does not offer senders for metric threaded ports.
9. Dual Station installations:
a. When replacing one gauge in a two station installation, the second gauge may need to be replaced as well.
b. Mixing two gauges from different manufacturers to one sender may cause an error in both gauges.
c. If one gauge fails the second gauge will read much higher than expected.
d. If sender fails "open", both gauges will read below 120F.
e. If sender fails "short", both gauges will read above 240 degrees.
10. Twin engines: It may be helpful in troubleshooting to switch either the senders or the gauges from engine to engine.

 

Wow. What a detailed response. Thank you so much! CSR participants are awesome.

 

Dave, You did not mention changing you raw water impeller... If did have not changed you impeller in the past three years or so, I bet that you have a bad impeller.

BTW do you keep your boat at Dillan's Creek? Brian (the owner) at Dillan's Creek has the same boat you have, he the best at diagnosing problems... I had an overheating problem this past spring, that Brian found was a collapsing raw water intake hose...

 

temp sensors do go bad... I had one side go bad while coming out of a transient marina during a week-long boat trip. It pegged the gauge and the alarm went off. I shut down, checked out the engine room and it all seemed good on mechanical gauges. Went back to their fuel dock and looked for replacement sensors at local stores thinking they have to be pretty generic Teleflex stuff. Local CAT dealer had them and left them in their pick up box for after hours pick up so we can continue our trip - gotta love the CAT service even if it comes at a pretty steep price, lol!

When you get replacements, make sure you get the right tem range and verify calibratation with either mechanical gauges (I have them on my engines) or laser temp gun. Also, make sure you have plugs ready when you replace them or you'll loose some antifreeze. Finally, I would recommend replacing both sides even if only one fails.

 

BTW do you keep your boat at Dillan's Creek? Brian (the owner) at Dillan's Creek has the same boat you have, he the best at diagnosing problems... I had an overheating problem this past spring, that Brian found was a collapsing raw water intake hose...

YES RCKNECHT, I do indeed compare notes frequently with Brian. We have had many similar problems over the last couple of seasons. I just thought I would test this problem at CSR.

 

Too bad that Dillan's doesn't let you paint your own bottom, otherwise I would put my boat there for the winter...

 

There are so many other advantages for docking at Dillon's.