Hurth HBW-50 Transmission Problem

[Jimriff]

Ahoy folks,
Re: 1980 O'Day 30, Hurth Transmission In Back of An M20 (16 HP) Universal Diesel.

Have been seeing evidence of either an oil or transmission leak for some time in the form of black speckling in the area under and near my engine. Had not tracked it down because at one point I found my oil dip stick not securely seated and thought it was an oil problem.
However, today, after having found that oil (or transmission fluid) had made its way into my bilge after what was a 3 hour motor run a few days ago, I was out for a sail and found the transmission making a fairly loud tapping noise with the turning of the prop shaft after we shut down the engine and were under sail.
For the last 9 years I've had this boat the prop shaft would make a very soft clicking sound that tracked with the spinning of the prop shaft when it was left in neutral while sailing, nothing that seemed to require attention. Today, however, this noise was much louder than usual, and was more like a loud tapping sound coming from the transmission, or maybe the bell housing next to it.
When I put the boat in reverse while under sail, the shaft stopped spinnig and the noise stopped completely. When I put the boat in forward, the shaft did not stop completely, but slowed considerably, and the tapping noise tamped down quite a bit. I do not recall that the shaft used to turn at all when I would put it in Forward gear while sailing with the engine off, so having the prop shaft fail to lock up when put in forward gear while under sail may be a symptom of a/the problem.
When we got back to the slip, I pulled the transmission dip stick and found the fluid down by maybe 25%, with some fluid wiped off from under the transmission. No evidence that the drain plug itself was leaking. I replenished the transmission fluid to its correct level and will be taking her out to see if that tamps down the clicking/tapping sound, however not sure what to make of the shaft not locking up when I put it in Forward while sailing, and of course I need to track this leak down
Any thoughts as to what's going on would be welcome. Have had some input that the likely transmission fluid leak may be coming from a leaking "seal", although I did not see any obvious evidence of where the leak was specifically coming from. Any idea what the clicking sound which is now the louder tapping sound might be?
Any input would be much appreciated...

Thanks much,
Jim
"Sojourn"

 

[Mike Holibar]

The transmission free wheeling while in "ahead" is not soemthing to be concened about. The oil loss and tapping sound together might indicate a bearing on the way out, possibly the oil is coming from the front main seal which, of course you can't see without removing the gear box. What is the condition of the fluid, does it look clean? Can you get a magnet on a stick down the dipstick hole to see if any metal particles are present.? Dirty oil or metal particles would indicate that you definitely need to remove the transmission for repair. Good luck,

 

[Jimriff]

Thanks Mike...

Thanks much for your response Mike. All the way from New Zealand, no less.
The transmissin fluid was in terrible shape. Pitch black. My fault for not having made sure it was changed more frequently.
Yes, I can and will get a magnet into the gear box to fish for metal. Hope not to get any bites...
Thanks again..

Fair Winds,
Jim

 

[kloudie1]

Couple of quick thoughts, Jim.. I agree with Mike in that the slipping is nothing to worry about but if the boat is sailed a large amount with the engine off and the transmission in forward, it will wear out the cone clutches and generate a lot of wear particles which make the oil really black! When in neutral and freewheeling, the lower shaft in the transmission turns but not the upper shaft so there is no rotation that would (should?) affect the forward seal or the flywheel. You are doing the right thing by changing the oil in the transmission!.. Don’t sail in forward gear with engine off!
Tapping noise.. Does the back end of the engine wiggle when the prop is freewheeling? If so, it may be misalignment of the shaft to tranny coupling, or a bent prop shaft.. The tapping may be a bad motor mount responding to the wiggling.. could be the prop shaft hitting the inside of the log where the log is fixed to the hull.. Could be the prop shaft thumping in a loose Cutless bearing in the strut.. Could be an out of adjustment shift lever that is not positioning the clutches correctly.. Lots of “could bees”
The most probable ones, are the Cutless bearing and bent shaft.. both of those can be checked while swimming.. I would get the shift lever adjustment checked as well, both at the transmission and at the remote lever in the cockpit. Good luck with the detective work, Jim.

 

[Stu Jackson]

When I put the boat in forward, the shaft did not stop completely, but slowed considerably, and the tapping noise tamped down quite a bit. I do not recall that the shaft used to turn at all when I would put it in Forward gear while sailing with the engine off, so having the prop shaft fail to lock up when put in forward gear while under sail may be a symptom of a/the problem.
When we got back to the slip,..

You're not supposed to put Hurth transmissions in forward with the engine off, only neutral or reverse.

See: http://www.c34.org/faq-pages/faq-transmission-position-sailing.html

 

[Jimriff]

New clues and data points...

Thanks all for the inputs. Much appreciate it.
Changed the transmission fluid today, used a magent to check for any metal in the transmission and found none, knock wood.
Then took a brief dive under the boat and checked my prop shaft mounted zincs as a possible alternative source of the tapping. Found the zinc installed at the beginning of this season by a diver to be loose on the shaft to the point of being able to easily slide up and down the shaft, and rattling a bit to boot. May be be the source of the tapping noise. Have the diver scheduled to visit the zinc soon to tighten it up on the shaft, hoping that is the source of the problem.
Also, no sign of the tapping noise while under power in Forward or Reverse, although the engine noise may be drowning it out.

Bullitens As The Happen,
Jim

 

[Jim N.]

Problem Solved!

Diver finally got to tightening up the loose zinc mounted on the drive shaft last week. That did the trick. Was under sail the other day for the first time since the zinc was tightened up, with engine off and the transmission in neutral, and voila! No more tapping noise.
Thanks again for all the input. Despite the relatively easy fix, everyone's comments were very helpful and instructive...

Fair Winds,
Jim

 

[Stu Jackson]

So glad to hear that

Jim, and the price was right, right? Given my post earlier about transmission positions, our experience has been that when sailing, if the transmission is in neutral the prop moves the shaft which makes a noise, so we use reverse. Just sayin'...