sending units

[jnuttall]

I have a 1978 53MY with 8V71Ts. I just wrapped up an inline rebuild of my starboard engine (fun) and now I'm trying to fix the water temp and oil pressure gauges. Mechanic said to try and find both sending units for dual station. The current gauges are AC and Sams doesn't carry. Does anyone have any suggestions for locating these? Thank you in advance.
Jeff

[GJH]

Lauderdale Speedometer in Ft Lauderdale. They are quite knowledgeable about these boats and engines.

[scottinsydney]

The AC oil gauges should be 0-90 ohms. For a twin station you can check this by connecting in parallel 4 x 45 ohm resistors, turning on the ignition and looking at the gauge. It should read 80 psi.

There is no 90 ohm sender now made with this rating. This 90 ohm sender was unique to AC gauges and prior to the introduction of American and European senders standards.

For a twin station sender replacement you require two VDO 10-180 Ohm 1/8 NPT senders attached to a T fitting and wired in parallel. This has the effect of reducing total ohms for a twin station to max 90 ohms.

This workaround was successful on both engines. Gauges read good enough and about 10 psi lower than the mechanical gauges at 900rpm. Accurate at 1200rpm.

Photos show:

- The T fitting and two new 10-180 ohm senders. Wire these in parallel, which means connect both wires from sender 1 to the terminals of sender 2, then connect the engine wires to sender 2.
- Four x 45 ohm senders to test the gauge is indeed 0-90 ohms. If so, both gauges will read 80 psi.
- Port engine running with new VDO senders installed.

[MVCaprice]

Scott that is great info.

If I could take a quess, I suspect your accuracy problem is likely due to the non linear curve of the VDO gauges. They post curves for each sender so that may or may not be helpful.

Do you happen to know if the AC senders are linear 0-90 ohm? I suppose if they are or frankly if they aren't that may explain the slight difference in readings on the gauges at different points in the curve.

[MVCaprice]

BTW, did you look at these senders:

https://dieselpro.com/engine-gauges-...de-aceite.html

They looked like a possible OE match, although I haven't reached out to see for sure...

[scottinsydney]

I don’t know if the old AC senders are linear or not. I thought my slightly lower difference might be brcause the single AC sender started at 0 ohms and now the twin VDO senders I used started at 10 ohm. ( I could not find a 0-180 sender.). All the sources I tried said the original AC Dual senders were no longer available including a company that spoke with an old AC tdchnician who now works for AC Delco.

[SeaEric]

Beede Electrical Instrument Company part# 127352 is a 0-90 ohm, 0-80 psi oil sender. It made my 1966 oil pressure gauge work again.

[MVCaprice]

Beede Electrical Instrument Company part# 127352 is a 0-90 ohm, 0-80 psi oil sender. It made my 1966 oil pressure gauge work again.

I have been looking for this and I found some alternate part numbers:

Part Alternates:

127352, 500532, 63631, 6620-01-197-7083, 01-197-7083, 6620011977083, 011977083

https://www.wbparts.com/rfq/6620-01-197-7083.html

I am very curious to see whether they work.

[jnuttall]

I appreciate everyone's input. I've passed the information along to my mechanic and he's going to trouble shoot a couple of things based on you input. Thanks
Jeff

[JonHupp]

I have been looking for this and I found some alternate part numbers:

Part Alternates:

127352, 500532, 63631, 6620-01-197-7083, 01-197-7083, 6620011977083, 011977083

https://www.wbparts.com/rfq/6620-01-197-7083.html

I am very curious to see whether they work.

Has anybody determined if these pressure sending units work and are available? This looks like MilSpec stuff so it may not be affordable or available in small quantities? My port sending unit is low and while having mechanical gauges in each engine room is reassuring, it would still be nice to have something closer to the real oil pressure showing on the helm gauges without replacing everything with VDO...
Thanks. Jon