Tranny temp gauge

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Dixie Life

Senior Member
Joined
Feb 4, 2011
Messages
221
Location
USA
Vessel Name
Aku Uka
Vessel Make
43’ DeFever
Happy and Merry to everyone. Spent my holidays in the engine room looking for a way to spend more money on my boat. I know, I’ll put temp gauges on my trannys. Now, where to install the senders. Any advice? Trannys are BW 72C. All advice welcomed.
 
I have thought about doing the same, and have same tranny.

I had looked at using one off of one of the pipe plugs, next to the over temp switch. It is easy if you want an electric gauge, but I wanted a mechanical in the engine room, which has made it harder.
 
Ir the transmission is heat exchanged, why not tee the line before going into the heat exchanger?

Ted
 
I am always amazed at the number of gauges and electronics some boat owners want on their boats. My first boat was a simple 23 foot Pen Yann. I had more junk at the helm then I would ever need. In fact I had so much stuff hanging in front of the helm I could not get a clear view for docking.

Keep It Simple Skipper

pete
 
I installed a 4 channel blue seas temp alarm/display. I only have one engine so I put sensors on the engine exhaust, tranny cooler, generator exhaust and generator block.
With twins, you could do both exhausts and both tranny coolers.
 
Just dug out my manual. It has a diagram of the optional temp sensor set but does not show installation location for the 2 sensors.:facepalm:.
If I remember correctly there are a couple of plugs near the breather but hopefully someone will post a photo of a trans with this option installed.
 
The PO installed a pressure gauge in one of the pipe fittings next to the vent on the top of the transmission. It works fine for the pressure but not sure if it will work for the temp.
 
Temp sender location

After burning out the same transmission when it had no temperature senders, I installed a high temp switch in the drain plug and a temp sender in the pipe plug just forward of the cooler return. I believe this plug is meant to test the fluid pressure.
 
Did the temp sender work in the plug for pressure readings? Also, OK I’m stupid. Where is the drain plug?
 
Did the temp sender work in the plug for pressure readings? Also, OK I’m stupid. Where is the drain plug?
I don't think there is actually a drain plug. I have temp sensors on my BW 72C's but won't go to the boat for another week or so.
 
Drain plug is on side of sump.
On mine the nut on plug is pointed forward, and threaded toward the stern. Can not see, but can feel it by reaching under it.
 
pics of trans temp sender and hi-temp switch

They sell a high temp switch with a 1/2 NPT for the drain plug. I used a Smith Warner trans sender and gauge for the test port.
 

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My 72Cs came from the factory with a temp switch for an overtemp warning. From what BW says, the fluid temp pretty much doesn't matter as long as it doesn't hit 190*. If it hits 190*, get it cooled down and change the fluid ASAP.
 
After burning out the same transmission when it had no temperature senders, I installed a high temp switch in the drain plug and a temp sender in the pipe plug just forward of the cooler return. I believe this plug is meant to test the fluid pressure.

Burning up a trans? Never heard of it. The source of heat is the only the engine to trans mounting, gears, the clutches and heat through the crankshaft as I see it. And the clutches only slip when shifting. How could it get too hot?

I had a 25’ Albin w a three cylinder Yanmar. The trans was WAY too noisy. Perhaps the Kanzaki gearbox being aluminum was a big player re the noise. I mixed the trans lube lube oil from several high viscosity oils one being a very high viscosity 2 stroke synthetic lube. And a bronze oil pump. There was some heat there but I couldn’t imagine it damaging the trans. The only friction was from the gears, clutches and heat transfer from the engine to trans where they are in contact. And there shouldn’t be any heat from the clutches unless they were slipping as they were designed to do when they were shifting.

The high viscosity oil did the trick .. much quieter.

How does a pleasure boat transmission burn up? With no oil/lube I can relate to that but heat as a destructive source w plenty of oil? As to temp monitoring I can’t see it. There must be something here I’m totally missing.
 
How does a pleasure boat transmission burn up? With no oil/lube I can relate to that but heat as a destructive source w plenty of oil? As to temp monitoring I can’t see it. There must be something here I’m totally missing.

If friction disks are completely worn out then there could be significant slippage that will create a lot of heat.

No oil will take out transmission. Unfortunately oil pump will maintain pressure and temp until there is zero pressure and thus no temp. By the time you notice your gauge you may have a destroyed transmission.

You might get an earlier warning by simply monitoring external transmission body temp with a very loud piezo alarm.
 
I always kept the cooling system in good condition, and whenever I measured temperature with a heat gun it was around 105/106 F. That was using 30 weight synthetic engine oil for lube in the BW71.
Therefore I never considered a temp gage necessary.
 
My friend's OA42 has tranny temp gauges in the engine compartment. They don't have telltales so I'm not sure what good they are. On a related topic, when I worked at a car dealership I did a Google search for tranny parts and got a visit from HR.
 
If you install it in a tee off of the oil line to the cooler, make sure it’s the output side! The other hose carries cooled oil back to the transmission.
I’d use a Murphy gauge with an alarm, or eliminate the gauge altogether and use an over temp switch to a buzzer.
Visit Aqualarm website, plenty of this type of things available.
 
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