ZF Transmission on a Hatteras 54

Thermostat/Thermistor?

Check the temp gauge/sensor/sender also.

Oil should run at a minimum temp, 194 is pretty good for keeping moisture out of oil. Thermostats (in airplanes we call the thermal valve that opens the oil flow to the oil cooler a thermistor), I don't know if that term or devices are used here which is why I put a question mark, but considering the oil heats up to a safe and proper operating temperature then maintains that level, I suspect it may be.

Stick to mudboats and race cars Henning.

Aircraft use a vernatherm valve to control oil temperature. A thermistor is an electronic device, a type of resistor that changes resistance with temperature.

You're right, it's a vernatherm, it's been 15 years since I was working on airplanes. I've been doing a lot of other things in the mean time. Why don't you just stick to your books in your brokerage office or contribute something worthwhile like the piece of knowledge that says, "yes" or "no" to whether it's a thermostatically controlled loop. You're such a condescending prick, I bet the brokerage company hired you into your position so no one would bother calling for support. Your kind makes me want to vomit. When was the last time you actually made it to sea?

now, now, kids.

What temperature does the other transmission run at when at temperature. What are engine temps on both engines?

I have seen some electronic diesels run fairly high gear oil temps. I have one boat with series 60's and the gears run at 154 degrees/ engines 169 degrees.

Is this really a problem? Maybe the other gearbox is heating up faster because of a running gear issue on that side? What does the manual speicify for oil temperature limits?

Your best bet is to contact ZF directly. There is usually no better source for troubleshooting information.

Actually if I remember correctly most of the computer controlled cats, the gear temps run very very close to whatever the engine temp is. I would call a CAT dealer and confirm with your model.

we have ZF BWs on the b oat i run, with 1412Es (1400hp, 2003) and one runs slightgly warmer at fast cruise (1850 to 1950rpm), usually by 11 degrees (169 vs 158). they run much cooler than the engines

it's always been like that and i haven't looked into it. i'm ASSuming there is just a little less flow on that side.

assuming your ZF is similar to ours, 194 is high. i'd look at water flow first. how is the tranny oil pressure?

also, if your impeller is starting to get worn, the tranny will be the first one to get warmer since on the engine side the Tstat will regulate temp. and you have excess cooling capacity you dont' have on the tranny

Actually, 194 is a minimum good temp to be running oil at. Below that it doesn't really get a chance to eliminate water from condensation and forms sludges. 194-225F is a very good temperature range for oil to operate at. Oil doesn't really start to degrade until in the mid 400s.

Keeping things, engines or gearboxes, too cool is not good. Any time you are operating either below 190 you are giving up efficiency (for engines) and causing problems.

The starboard side wouldn't be running in reverse would it?

Again, contact ZF with the precise dataplate information off both gearboxes and get back to us.

i don't see what the temperature at which oil will start degrading has anythign to do with this discussion, there are many things in a tranny that will fail before the oil does!

i pulled the ZF BW190 series manual to double check, alarms are supposed to go off at about 200deg F. running 190+ would be too close for comfort.

If the OP's trannys are similar to the BW190s (and the 211), 194 is too hot.

Running below an alarm setpoint is perfectly acceptable. A warning is just notice that a parameter is approaching a limit and should be observed, it is not a limit itself.

I just looked at a range of ZF gearbox specs and all of them provided a technical page giving pressure and temperature limitations and settings.

What ZF describes as "nominal" temperature for pleasure, light, and medium duty applications is 90*C (194*F) and for continuous duty applications, 100*C is nominal. In trailing mode with a trailing pump, 75*C (167*F) is nominal and without a trailing pump the upper limit is 105*C.

The warning device is set between 95*C (203*F) and 105*C (221*F) depending on application.

min temp is listed as 30C in the manual so that's a wide range of acceptqable temp

my point is that if you're running at the upper end of the range in "normal" conditions you are close to going too hot as soon as something happens or changes since you have no reserve cooling capacity. a minor restriction, loosing a vane on the impeller, warmer sea water temp, etc...

pick something in the strainer and you will jump over the limit.

there is nothign in the manual indication that you should be operating at the top of the heat range. not a good idea in my opinion.

that said, i notice that it is his port tranny which is running a little hotter... in my case, the port is also running a little higher as mentioned, 169 vs 158. maybe it's a rotation issue...

There is actually, ZF describes 90*C (194*F) as "nominal." Nominal means the designed operating point. It is the temperature at which the oil viscosity creates the least amount of drag while still providing adequate lubricity.

The warning point is where the manufacturer says you should pay attention to the operating conditions. Given that the nominal point of 90*C is well below the 100*C considered nominal for the same unit in continuous duty service I don't see any issue at all.

If you want to get the best performance from a machine you have to operate it near its limits. The designer determines the limits that, if not exceeded, will assure long life. If you fear the limits you have to buy larger machines than you need and operate them at lower efficiency to obtain the perception of safety or whatever you feel you are sacrificing.