Transmission Fluid

Tom Lanzilli · November 24, 2007, 04:47:57 PM

My C34 MKII has a HBW 150 transmission; the operator's manual tells me the sump capacity is .59 U.S. qts. This year for some reason I took the time to measure the amount of fluid I pulled from the transmission and the amount it took to refill the unit. .59 qts. = 18.88 ounces. For some reason the transmission only took 6 ounces to bring the unit full. Puzzled at this point I emptied the transmission a second time and again refilled the unit with again the same results.

I can not explain this, the boat is on dry land, and it does seem to be sitting fairly level. Has anyone ran into this or have an explanation?

sail4dale · November 24, 2007, 05:13:58 PM

yep, same here! I don't believe we get the transmission really empty when we suck out the oil. That's about the only reasoning that seems to apply.

Ron Hill · November 24, 2007, 05:45:53 PM

Tom : Dale is correct. If the Xmission is completely dry then .59qt is the amount that will fill it to the correct level. The xmission is at an incline so you can't get all of the fluid sucked out!

Do what I learned 20 years ago. Get the level to the correct amount - then suck out all you can suck out. Sometimes you have to fool around with the hose so it's all the way at the bottom. Measure that sucked out amount , mark a container and then that's the amount that you must add to obtain the correct level!! A thought

Tom Lanzilli · November 24, 2007, 06:05:03 PM

Ron actually the reason I measured the amount I took out was to do exactly as you pointed out. The thing that really puzzles me is this is not a big unit and if the total capacity is 18.88 ounces how come I can not pull out more than 6 ounces. The difference seems to large to make sense.

Stu Jackson · November 24, 2007, 07:34:53 PM

Tom, I suggest you carefully check the Hurth manual. My Hurth manual (1986) covers the HBW 150 and shows that the amount of fluid required is 0.55 LITERS not quarts (although close).

Ron's right about the angle and how to refill. I do BOTH: measure what we take out, refill that amount and also check the dipstick.

In addition, my understanding is that those who winterize their engines fill the entire transmission housing, then drain it out and refill to the proper amount in the spring. Obviously, we have never had to do that.

Just to remind folks of information that has been posted over the years: There was and remains an error in the Universal engine manual (posted on this site) on page 41 about the amount of fluid required for the M25 engine transmissions (either HBW 50s or HBW 100s).

Manual WRONG: 1.3 pints (.55 liter)

CORRECTION: .73 pints (.31 liter)

Newer HBW 150 transmissions for the larger engines state 0.55 liter. This is a 1986 Hurth manual, so check the newer manuals that come with your own engines to confirm.

I just do not like the liter, ounce, pint conversions - one of these days I'll do it and write it down! Spoken like a true engineer

As far as the difference you are reporting, I've found it hard to be assured that our "sucking hose" is always at the aft end of the transmission housing. I haven't ever that carefully measured the amount we take out, but it's usually just a bit less than three quarters of a good sized 8 or 10 oz. plastic drinking cup. The color of the removed fluid compared to the new stuff makes me feel much better when it's been replaced.

Breakin Away · November 19, 2018, 03:57:35 PM

This is a very old thread, but its potentially incorrect information caused me a lot of confusion, so I'll post a correction to avoid others wasting time on this issue.

Not all M35B motors have the Hurth HBW 150 transmission. My boat (#1535) -- and after researching other threads, it appears that most MkII boats -- have a HBW100 transmission. Transmission fluid capacity is 0.33 quart = 10.5 oz. That's a little over half what's reported in this thread, and accounts for most (but not all) of the discrepancy.

Hull #1660 is the only one I've seen that reports a HBW 150 - all the others I've seen report a HBW 100 or ZF 10M (same thing). Maybe there are others who can report their actual transmission model so we can get a broader understanding. But bottom line, don't assume your M35B has any particular model of transmission. Remember, "If you read it on the internet, it must be true" (not)

Also, my drain plug is not in the low point of the sump, so there's a good chance that sucking out the oil with a tube will get more than the drain plug, if the hose is properly positioned. I am not able to accurately measure the amount that comes out because my pump sucks into a 3 gallon pail. But when I hunt around with my tube I do get to lower points that pull additional amounts out.

Also, my manual recommends filling the transmission completely with oil only if storing for over 1 year. I have not done that because I'm afraid I'll forget to empty properly before launch.

Breakin Away · November 20, 2018, 05:00:43 PM

One other thing: Although my electric suction pump prevented me from measuring how much fluid I sucked out, I got EXACTLY 3 oil changes (to the last drop in the bottle) out of my quart of Dex III. So I was right at the 0.33 qt spec for fluid capacity of the HBW100. My little Teflon pump tube must have been getting to the very bottom of the oil sump.

Noah · November 20, 2018, 05:13:25 PM

Breakin— how often do you change your transmission oil? Must have been keeping that one quart for a long time to warrant 3 changes?

Breakin Away · November 20, 2018, 07:46:16 PM

Quote from: Noah on November 20, 2018, 05:13:25 PM
Breakin— how often do you change your transmission oil? Must have been keeping that one quart for a long time to warrant 3 changes?

End of every season, at the same time I change the motor oil.

Jim Hardesty · November 21, 2018, 07:51:18 AM

FWIW I change my transmission fluid every season. A quart is good for about 3 changes. Took me a while to find the right extracting hose and fill funnel, now the changes are mess free. And rember the fluid gets checked with the dipstick unthreaded, just set the dipstick in place then remove and check.
Jim

mark_53 · November 21, 2018, 12:33:33 PM

Quote from: Stu Jackson on November 24, 2007, 07:34:53 PM

I just do not like the liter, ounce, pint conversions - one of these days I'll do it and write it down! Spoken like a true engineer

Stu, No need to remember or write down. Just ask Siri (or Alexa or Goggie).

Stu Jackson · November 21, 2018, 12:59:12 PM

Quote from: mark_53 on November 21, 2018, 12:33:33 PM

Stu, No need to remember or write down. Just ask Siri (or Alexa or Goggie).

I'm convinced that "dating" is no longer viable for me.

Spreadsheets, on the other hand, are always useful.

Ron Hill · November 21, 2018, 01:45:42 PM

Tom : Every year at winter layup, I fill the transmission to the top with transmission fluid. This keeps all of the seals wet and combats any chance of condensation.

Then in the spring I suck out all the fluid and refill to the correct level.
Transmission fluid is cheap and a quart lasts a couple of years because you use so little!!

A few thoughts