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Temp/oil sending units

mattv

Contributing Member
Anyone have a good source for dual station oil pressure and temp sending units? I am having trouble finding the proper ohm range for my new gauges.

Thanks,

Matt
 
West Marine sells them--if you can afford it!

Jeff

PS: Better test the temp switches before trusting your motors to them. I went through at least TEN before finding a couple that worked.
 
Thanks all for the input, I found them at boaterslandmarine.com . 95$ including for oil and temp for both engines... I still dont under stand the difference between the singe and dual staion sensors but Faria says I need them.

Matt
 
A typical single gauge Teleflex or Faria oil pressure sender should show a resistance of 33 ohms (full gauge pressure) to 240 ohms (zero gauge pressure). A dual gauge sender will show half of those resistance values. But these values are only good if measured directly at the sender with the boat gauge wiring disconnected. The wiring between the sender and the gauge on a boat can add a lot to these resistance readings and make the gauge read inaccurately.

My 34 ft. Silverton has about 50 feet of 16-gauge stranded wire between the starboard engine and the oil pressure gauges at the upper and lower steering stations. The port engine is probably about 8 feet longer. Then there's the resistance added by the connector between the wiring harness and the engine wiring. Depending on the amount of corrosion that has built up on the connector contacts, that could add a few more ohms. The result is, when you measure the resistance of the sender and all the boat wiring, the 33 ohm full pressure resistance could be 40 or 50 ohms or even more and that will make the oil pressure gauge read lower. You can see just how much error is being added by the boat wiring by connecting your new gauge directly to the sender on the engine.

Another thing to remember is that marine gauges aren't precision instruments and the scale shown on the face of the gauge is there for appearance rather than accuracy.

Bill
 
I appreciate all the info and replies, I also need temp and oil pressure swithches for the alarms. Can anyone suggest what temp the switch needs to close at? And what psi the the oil pressure switch should activate? Fresh water cooled 318's.

Thanks,

Matt
 
..... I still dont under stand the difference between the singe and dual staion sensors but Faria says I need them.
Matt
Matt, both helms are in parallel with one another. This changes the resistance that the sender must be capable of.
Trust us..... your system does require the dual station senders.


...... I also need temp and oil pressure swithches for the alarms. Can anyone suggest what temp the switch needs to close at? And what psi the the oil pressure switch should activate? Fresh water cooled 318's. Matt
Define "Fresh Water Cooled". Some refer to a "Closed Cooling" system as FWC. If Closed System cooled, your operating temperature should be close to 160*/180*.
Marginal oil pressure may be 15-20 psi (or so) at low rpm.

I think that these switches are available in an array of temperature and pressure settings. So you should be able to choose which temperature, and which low oil pressure setting, you wish for these to close.
If memory serves me, some of the Hobbs or SW oil pressure switches are adjustible to a certain degree.

.
 
About 200 ' F for the motor, and 160 ' F for the exhaust system.

Jeff

PS: I had to go through a dozen NEW temp switches before I found two worked correctly, so be sure to test every one of them.
 
Jeff,
my boat never had alarms forr the exhuast, where do you suggest I install them? Manifolds or elbows or risers? Ricardo to answer your question the engines have a closed cooling system.

Thanks,
Matt
 
Ricardo to answer your question the engines have a closed cooling system.
Matt
Matt, that answer that question. Your best engine temp, IMO, will be 160*/180* since you have the closed cooling systems.

Now, there is another question that brings up exhaust manifold temperature. Are you in salt water?
You'll want to know that salt water begins a crystallization process at/near temperatures exceeding 143*, I believe. This would be a reason to keep your "spent" sea water temps as low as possible.
This issue becomes the scale that builds within the exhaust system, from the crystallization. It may not be a complete deal breaker, but it may shorten the usable life span of your exhaust.
 
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