Page 31 of your engine manual....
Dextron II or III type ATF.
Amount depends on your transmission type...

At least on my MK II with M35A, the only way to get the old oil out is to suck it out. I have a big plastic syringe with a plastic hose that I stick into the dipstick hole as far as it will go. If there's a drain plug, I've never found it and it would be difficult to catch the oil in any event.

Filling it back up you check the level with the dipstick just inserted, not screwed in. This may vary with transmission type, so I'd check the manual as in the prior post.

I've changed mine on my 1994 MK1.75 and I did it the same way as Gary did, inserting a liquid pump hose in the dip stick hole. (got a nice little hand pump at Harbor Freight Tools for cheap).
The dipstick is really hard to read cause the fluid is clean and clear.
Not a hard job as I recall.
Sam

Mine is M35B engine. Amount is 12 oz - size of a beer can. Type is Dextron II or Dextron III automatic transmission fluid. To remove I use a 2 oz syringe from A drug store and I add 1/4" plastic tube about 12" long. The syringe is for basting turkey. To add oil I measure the amount in a container then pour it in. I replace the oil every 100 hours or every season. The info appears on page 34 of my manual. I am including a copy of page 34.

If you are storing your boat on the hard in winter ZF-Hurth recommends filling the transmission for the storage period, then sucking the excess out in spring. I've seen several different values for the amount of working fluid in several ZF-Hurth publications, it seems to be around .35 litre for the HBW100. There is a repair manual for theseZF-Hurth transmissions in the Members section on the main site

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I use a Pela oil extractor for both the trans and engine oil. It is without a doubt the best device I've ever used for this purpose. Had one of the 12V bucket mounted pumps and this Pela is way better. Holds enough oil that I can do the engine and trans at the same time and just carry the ball away to the waste oil facility.

These transmissions work pretty hard and I think they are marginal for our boats although nowhere near as bad as the HBW50 was in the 28. I use synthetic ATF in mine, for the cost of a litre a year of fluid it is cheap insurance. The heat build up will kill conventional ATF quickly. Most reputable rebuilders will suggest synthetic ATF to increase trans life. You can get a cooler kit for these transmissions as well.

Regarding the difficulty of reading the dipstick...I calibrated a popsicle stick to the dipstick and use that to check the level as I am refilling the transmission. Just wrapped some masking tape around the appropriate level on the top of the stick to simulate the threaded section of the dipstick.

[QUOTE=Molly Malone;17041]Regarding the difficulty of reading the dipstick...[/QUOTE]

Or just roll the dipstick on a piece of paper towel.

There's no filter on the small Hurth-ZF transmissions that I am aware of. There's no pump that I am aware of, pretty sure they're splash lubed. As always, I stand to be corrected. I hope I'm not wrong on that, if I am I have missed what would be an important maintenance point.

No worries, Bud, you're right.