Why am I changing Hurth gear oil?

[Skipper]

This is my 2nd time changing the gear oil in the Hurth HBW 50. Universal M18.
Interval 2 years and about 100 hours.
It's also the 2nd time that the oil has come out exactly the same color, consistency and smell as the new oil going in.
So why am I changing it?
The boat has mediocre engine access at best, and there are a couple areas which are inaccessible; the bottom of the gearbox being one of them. Even if I could get the drain plug off, there's no way to get a recepticle under it. So have to suck it out the top with a hand pump. Not a terrible job, but awkward and cramped.
This is the same gearbox used behind other motors up to 25hp. Mine is 14hp. This may be why the oil stays good, with light duty and never getting heated up.
Any comments. Beat me up if you like

 

[Ken Cross]

100 hours for transmission fluid seems like an awfully short interval.

Ken

 

[Stu Jackson]

Simply extend the intervals SLIGHTLY and keep checking.

http://c34.org/bbs/index.php/topic,5139.msg31528.html#msg31528

We all take it out of the top. There's a non-reusable crush washer on the bottom.

If you let it get too dirty, what's your transmission worth to you?

 

[Skipper]

100 hours for transmission fluid seems like an awfully short interval.

Ken

It does. But Hurth and others say change every year. Or 250 hours. I waited for 2 years. I think the 250 hours mark might be more logical, but with routine checking to make sure.

 

[Benny17441]

No you are right. A transmission does not raise pressure, has no combustion byproducts, its inside is an enclosed space, free of dust and outside contaminants and only exposed to moderate heat. A well broken-in transmission will produce very little metal shavings so other than viscosity breakdown due to friction and heat there is no reason to frequently change the oil. Adding to that is the moderate use our auxiliary engines receive in a year. I basically check the oil level every two months or before going on a trip and I will rub a dab of the oil between my thumb and forefinger to check for viscosity and color and if they are OK unto the next couple of months. Can't remember when I last changed it, at least 5+ years. I have considered Synthetic oil as is much more resistant to breakdown so that in theory I would not have to change it again ever but since regular oil is doing such a good job why bother. There have been some reports about synthetic oils being the cause of oil leaks in older engines; maybe it has to do with elevated oil pressure which would not affect a transmission but why chance it.

 

[Skipper]

We all take it out of the top. There's a non-reusable crush washer on the bottom.

I was curious of how others did it. TY.
I don't want it to get dirty. Hence my routine. My transmission is worth a lot to me, so I stuff my middle aged a-little-less-than-lithe body into the sail locker occasionally to hold a small hose in one hand into the gearbox top while holding a receiving jug and other hose end with my foot against an engine stringer, while bracing against the hull and fuel tank with my elbow and other foot, and pump away with the other hand while holding the pump bottom with 2 free fingers from the hand holding the intake hose.
I'd have taken a picture for laughs, but no usable appendages left for a camera.

 

[Skipper]

No you are right. A transmission does not raise pressure, has no combustion byproducts, its inside is an enclosed space, free of dust and outside contaminants and only exposed to moderate heat. A well broken-in transmission will produce very little metal shavings so other than viscosity breakdown due to friction and heat there is no reason to frequently change the oil. Adding to that is the moderate use our auxiliary engines receive in a year. I basically check the oil level every two months or before going on a trip and I will rub a dab of the oil between my thumb and forefinger to check for viscosity and color and if they are OK unto the next couple of months. Can't remember when I last changed it, at least 5+ years. I have considered Synthetic oil as is much more resistant to breakdown so that in theory I would not have to change it again ever but since regular oil is doing such a good job why bother. There have been some reports about synthetic oils being the cause of oil leaks in older engines; maybe it has to do with elevated oil pressure which would not affect a transmission but why chance it.

Thank you. Yep it almost seems that I might introduce more contaminates by opening the top than by leaving it alone.
I do recall that MainSail adamantly advised changing every year. I'm curious on his reasoning.

 

[Stu Jackson]

I have considered Synthetic oil as is much more resistant to breakdown so that in theory I would not have to change it again ever but since regular oil is doing such a good job why bother.

Just for newbies: some transmissions use motor oil and some use ATF, two very different materials.

 

[Calif. Ted]

Well Skipper, At one time anyway, ATF was Hygroscopic, so thinking was: it's sitting in the bottom of a boat in 90% humidity so the only way to prevent corrosion is to change once a year. When I had an HBW50 I felt the yearly change was just good practice also. BTW I used to have a turkey baster that had a long stainless tube that worked very well.
http://www.homebrewsupply.com/stain...VkD_p-1FWQZFapDlrn50Tu2ypmid9iMzpoRoC_APw_wcB
The following is from Wiki
Dexron-II, IID and IIE[edit]
Dexron-II was introduced in 1972 with alternative friction modifiers such as Jojoba oil. However, it caused problems with corrosion-prone solder in GM's transmission fluid coolers;[2] accordingly, corrosion inhibitors were added to the product. The resultant fluid, released in 1975, was called Dexron-IID. However, the corrosion inhibitor made the new fluid hygroscopic, which while it was not a major problem in automatic transmissions, made Dexron IID unsuitable for other hydraulic systems in which it was commonly used.[2] A further reformulation, to address excessive hygroscopicity (reference needed), but primarily to improve low temperature performance (20,000cP @ -40C vs 50,000cP@-40C for Dexron-IID) was named Dexron-IIE (GM Spec GM6137M).

 

[Ron20324]

[QUOTE... MainSail adamantly advised changing every year. I'm curious on his reasoning.[/QUOTE]

I think mine uses less than a pint?

 

[Skipper]

[QUOTE... MainSail adamantly advised changing every year. I'm curious on his reasoning.

I think mine uses less than a pint?[/QUOTE]
Yes, mine takes a little over 10oz.

 

[Skipper]

Well Skipper, At one time anyway, ATF was Hygroscopic, so thinking was: it's sitting in the bottom of a boat in 90% humidity so the only way to prevent corrosion is to change once a year. When I had an HBW50 I felt the yearly change was just good practice also. BTW I used to have a turkey baster that had a long stainless tube that worked very well.
http://www.homebrewsupply.com/stain...VkD_p-1FWQZFapDlrn50Tu2ypmid9iMzpoRoC_APw_wcB
).

Thanks, Ted. Now I can borrow your baster. :-D
I had trouble getting past the gears to the bottom with the small pump hose. Had to rig a smaller diameter plastic tube to the pump hose. Seems the baster would be too big? I guess not, you used it.

 

[chrisings]

Well Skipper, At one time anyway, ATF was Hygroscopic, so thinking was: it's sitting in the bottom of a boat in 90% humidity so the only way to prevent corrosion is to change once a year. When I had an HBW50 I felt the yearly change was just good practice also. BTW I used to have a turkey baster that had a long stainless tube that worked very well.
http://www.homebrewsupply.com/stain...VkD_p-1FWQZFapDlrn50Tu2ypmid9iMzpoRoC_APw_wcB
The following is from Wiki
Dexron-II, IID and IIE[edit]
Dexron-II was introduced in 1972 with alternative friction modifiers such as Jojoba oil. However, it caused problems with corrosion-prone solder in GM's transmission fluid coolers;[2] accordingly, corrosion inhibitors were added to the product. The resultant fluid, released in 1975, was called Dexron-IID. However, the corrosion inhibitor made the new fluid hygroscopic, which while it was not a major problem in automatic transmissions, made Dexron IID unsuitable for other hydraulic systems in which it was commonly used.[2] A further reformulation, to address excessive hygroscopicity (reference needed), but primarily to improve low temperature performance (20,000cP @ -40C vs 50,000cP@-40C for Dexron-IID) was named Dexron-IIE (GM Spec GM6137M).

Huh, well you learn something every day. An aside, the brake fluid in your car is still hygroscopic and most car manufactures recommend changing every 2 years regardless of mileage. (a loss of brakes on your car will make a bad trans on your boat seem like child's play). Anyway, my 2 cents. For those of use that need to winterize our boats need to over fill the trans with fluid to keep the seals, and more importantly, the clutch discs moist. Therefore commissioning the boat in spring includes draining and refilling the trans with fresh fluid. Boats are different from cars since, most of ours I suspect, spend many hours, days, perhaps weeks of inactivity. That is harder on mechanical systems then constant running and requires special maintenance schedules.

 

[FastOlson]

I solved the "one shot crush washer" problem last year. I also have a Hurth 50 trans, and they have a reputation for being fragile, so changing the lube oil every year seems like a really good idea.
http://www.ericsonyachts.org/infoexchange/entry.php?213-Hurth-17-mm-Drain-Plug-washer

That's the whole idea of 'preventative maintenance' anyhow.

Loren

 

[Benny17441]

It has been a while since they adopted a dual braking system in automobiles. The master cylinder has a dual reservoir, individual pistons and individual fluid lines alternate to wheels on both sides of the vehicle. The incidence of a total loss of brakes in cars at present is almost nil. By the same token, oils and transmission fluids have improved considerably in the last few years and maintenance schedules could be revised accordingly.