ZF Transmission on a Hatteras 54

If they're set up perfect, you'll never have to buy a new one....

Possibly to allow for build-up in the heat exchanger as time goes on, old gear oil that some people neglect to change, etc etc.

I don't know, ask ZF or Cat. I don't presume to know more than ZF's engineering department, I just quoted their numbers. If you are looking for some kind of battle, take it to them.

Besides, last time I looked, 150*F was almost exactly halfway between ZF's minimum of 30*C and max of 105*C. That is called the middle of the range and few technically literate people would call that "too cold."

You have a safety margin, that is what the alarm setpoint is for. It tells you to monitor the condition, not panic and call for a tow. If the temperature continues to increase you find out why, or reduce the power going to the gearbox.

Have you given any thought at all as to why the continuous duty temperature rating is as high as the maximum temperature allowed for pleasure use? It's because at lower loads the system can safely and continuously operate at much higher temperatures.

As an operator you should be aware of what limitations and warnings mean and not make decisions based on faith, superstition, or what sounded good at the bar.

Another reason the operating temperature will be between 30 and 90 deg C oil temp or such a large range, is because the seawater temp cooling the oil will have a large effect on how much heat the gear oil retains. If you're operating in a seawater temp of 40 degrees F, the gear oil will run much cooler then with a seawater temp of 90 degrees F.

Take your transmission cooler, sea-water cooling hoses off and physically look inside the transmission cooler to see if there is a lot of scaling and debris inside. It probably could use a good cleaning or acid wash. What does the other transmission temperature run at?

It sounds like your gearbox is having a nice day.

A gearbox typically absorbs around 3 percent of the power put into it. That means if you put 1000 hp into the front end, you will get 970 out the back and almost all of that 30 hp is converted to heat. In the example given, that is about 1300 BTUs per minute that the cooling system has to remove to stabilize the temperature.

Put less power into it and it runs cooler, put more power in and it runs hotter.

Thanks for the confirmation.

As the old saying goes ... "sometimes a cigar is just a cigar." I have found over the years that not everything that looks like a problem is a problem but you can always find someone to tell you the end is near.

This is true, but you're mis-understanding my post, I never said anything about one particular location. That particular Caterpillar 3412 could be in a vessel in Maine or Canada with a much lower Seawater temp, as it could be in Costa Rica with a higher seawater temp. Sportfish generally travel a great deal. This is why the operating range of the gear oil has such a large acceptible variance from Caterpillar. And if that particular seawater temp was 40 degrees F, and 90 degrees F, the gear oil would run at a totally different temperature.


As for your temps, they seem fine. The port gear on most or a lot of the vessels I've run tends to run about 10 degrees F hotter. And, with your location and water temp it seems to be running about where it would be expected to run......Although oil pressure seems a bit lower then it should be.....the Port is at 205lbs and starboard is at 250lbs......Do the transmissions have a filter? and has the filter been cleaned recently and oil changed?

You may want to pull the filter/scraper assembly out, I believe it is 4 bolts on a ZF, and the entire stainless steel drum slides out. Then spray it with brake fluid and hose it off. ZF recommends this every 1,000 hours and that is how the ZF dealer did it, there is also a drain bolt you can remove near where you turn the filter scraper, and you take that out after turning the scraper and alot of the debris will drain out (about a pint of oil drains out of it usually). Look up your model online and it should show the schematic.

Brake Fluid, or something like CRC Brake Clean?