Technical Reference Manual
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. (cont'd. on next page)
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 & Oil Temperature
Sender Identification Guide
Use this chart for field identification of Teleflex water
temperature senders. (ID code stamped on wrench
hex of sender. See illustration at left of chart.)
System (Inboards &
- 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.
- 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).
- If sender is shorted (0 ohms) gauge will read
- If sender has infinite resistance (Open) gauge
will read below 120F.
- If the gauge reads lower than expected, was
sealer used on the sender threads? (See
- The accuracy of the system (gauge, sender,
voltage range) can vary as much as 16 degrees at
- 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
- Teleflex does not offer senders for metric
- Dual Station installations:
- When replacing one gauge in a two station
installation, the second gauge may need to be
replaced as well.
- Mixing two gauges from different manufacturers
to one sender may cause an error in both
- If one gauge fails the second gauge will read
much higher than expected.
- If sender fails "open", both gauges will read
- If sender fails "short", both gauges will read
above 240 degrees.
- Twin engines: It may be helpful in
troubleshooting to switch either the senders or
the gauges from engine to engine.
Water Temperature Monitoring- Outboards
- The temperature monitoring kit includes all
parts to adapt to any of the situations noted
above. Yamaha engines will require an adapter
P/N 61886P in addition to the kit.
- Outboard engines use raw water for cooling
and are mostly aluminum, so they operate
cooler than stern drives. Consult dealer or
engine manual to determine maximum
operating temperature of your engine.
- The sender in the kit has 1/8-27 NPT threads
with I.D. Code "10" or "60" stamped on the hex.
Senders stamped "230" won't work correctly.
- Part number of the sender is 52320S010; the
flat bracket is 54552; the Z bracket IA55009.
- Some engines include a threaded hole directly
into a water line. The temperature sender can be
threaded into the hole, using no sealant on the
threads. The threads create the electrical ground.
- Some engines have a blind threaded hole for
a temperature sender that does not enter the
water jacket. After applying thermal compound
to the hole, thread the sender in snugly, again
using no sealer.
- Some Mercury engines have a blind hole
flanked by two bolts. These are for tightening
the flat plate. First place thermal compound in
the hole, then drop the aluminum spacer in the
hole. Thread sender into bracket over hole until
it hits spacer.
- The Z bracket installation is used most often as
it fits any engine. The Z bracket through hole is
held by any one of the engine's cylinder head
bolts. The sender is threaded into the bracket's remaining hole down against the cylinder head.
Scrape the paint from the head under the
sender to get good thermal transfer.
- The kit is supplied with one sender. If a sender
is desired on each cylinder bank on V type
outboards, a double pole ON-ON switch must
be used to switch sender input to the gauge.
The gauge can not accurately handle two
senders at one time.
- Testing the gauge for operation: Connect a
hot wire to "I" and ground wire to "G". Gauge
should read below the C. Next, Short the "S"
terminal to "G". The pointer should go above
the H. If the pointer sweeps this way, the
gauge is fine.
- Testing the sender: At room temperature, with
no wires on the sender, it should measure
approximately. 600-800 ohms on test meter.
- Replacement outboard sender IA96035 cannot
be used with this gauge. The gauge will read
very high. IA96035 is only for pre-1995
Johnson/Evinrude engines with a 50-250F