Any Play in Your Transmission Shift Lever ? (ZF)

[sgtPluck]

Hello again,
I am still trying to solve the mystery of why my transmissions keep failing (on my third ZF10/HBW100 now) I think I've ruled out everything but two remaining possibilities for the cause of the trouble. I'd appreciate it anyone who has a ZF/Hurth gear could comment on this first one...

There is a small amount of play in my shift lever on the gearbox. When I have the gear in neutral at the helm station the lever could be just under a centimeter forward or aft within neutral position. Do you have the same thing on your ZF gear? (I'm wondering if there's any chance my clutch plates could be touching when I'm charging - although there is zero movement of the shaft)

The second possibility I'm considering is that my propeller is about 6 inches from the keel (with no strut) I'm wondering if this is further than it should be, and possibly inducing wobble. It seems unlikely, as the whole shaft is only around 1.5 feet long.



Thanks for any input.

[GordMay]

Yes, the prop is too far from the bearing.
See Propeller Clearance Diagram - Cruisers & Sailing Photo Gallery

[sgtPluck]

Wow, thanks Gord, according to that diagram I am way off. Any opinion on whether this could be the cause of burning up transmissions?

[Astrid]

I would think (and I could be wrong), that you would show abnormal signs of wear to the cutlass bearing and stuffing box before trouble showed up at the transmission if the prop or drive shaft were unbalanced or out of round enough to cause transmission problems. But I agree with Gord that you have too much shaft unsupported by the cutlass or through hull bearing.

Once a little wear did show up, wobble would increase, then you would be damaging the transmission, and Hurths are a bit fragile and don't like that sort of thing. They also don't like any unexpected shocks such as debris hitting the prop or dragging through mud or sand if your ground, so a flex coupling is a good idea.

Here is a link to some suggestions for coping with Hurth transmissions:

Tech Tip #48 - Tech Tips - Shop Kinks & Tech Tips

[Zoomer]

You might check;
http://www.cruisersforum.com/forums/...es-8248-7.html

Also;
Alberg 37 Owner's Association
(see Project Database)

I have 2600 hrs on my Hurth, no problems yet-Good Luck.

[sgtPluck]

There is certainly no discernable wobble in the shaft. My measurements have not been scientific, I've just rested solid items on the shaft and felt for vibration. I feel no difference between being in neutral and the shaft turning, it seems very smooth. If the prop being too far back from the bearing causes slight vibrations that are enough to overheat the gear then that could be the issue, but without knowledge of whether this is the likely cause then I'm still just guessing. I think a proper test with a dial indicator will be one of my next steps.
I can get the shaft length fixed, but I think that might require a haul-out, so it will add to the expense.



thx

[Astrid]

Just a thought here, but at low rpms you may not detect any distortion at all, but a spinning shaft with as much unsupported length as yours has, may only begin to distort at higher rpms. Lower the rpms again it might well come back to true leaving you to wonder what has been going on.

[brutb]

Astrid, you little sailing winch, I whole heartily agree with you, that much shaft exposed with that size prop will cause exceessive vibration and oscillations. I would think that the drive coupling will have to be loosened to check the cutlass bearing. It would be near impossible to do it with it still coupled to the trans.
Good luck with the tranny problem. But Astrid, the NWP vixen is right...

[perchance]

The prop will whip at higher rpm if it is the slightest bit out of balance.

[Islander1]

Originally Posted by perchance

The prop will whip at higher rpm if it is the slightest bit out of balance.

Also "any slight growth" on the prop can throw it out of true!.
Those effing Barnacles will grow on anything in short time especially in the Tropics..I Anti fouled my boat prior to crossing the pond from the Canaries and when I arrived Barbados I had a "vegetable farm" below my waterline.

[S/V Antares]

Shure the prop is too far from the bearing however I doubt this is the reason the trans failed. The play in the lever is normal. Once the "Dogs" engauge you can still move the lever forward. (or backwards) The typical failure is due to heat. Often from overproping. What is your max rpm in gear? What is your max rpm out of gear?

Power shifting (Shifting above idle speed) will shorten the life expectancy quickly. When I got my boat the gear was bad, burnt oil etc. I took 2 inches off the pitch and never see more than 140 deg F.

[oldcal46skipper]

You did not state how many hours.
ZF's/Hurths are usually 1,000 hour gears. Check out Dr. Diesel on Foley engines, "Yahh, they are the $1 an hour gears, they cost about $1,000 and last about 1,000 hours."

YMMV

[Tynesider]

You do not say if you also changed the 'drive plate' when you changed the gearbox, this is a must unless you know how old it is, also fit the drive plate like a car wheel so you tighten each opposite screw in turn before tightening fully all.

We also spent hours trying to adjust the control cable setting before we changed the gearbox (also ZF 10) before we decided the box was the problem, but our box is at least 16 years old so I do not buy the comments they do not last.

If your shaft is only 1ft 6" long then I do not think the shafts your problem, one small point is make sure you get the location of the control cable connected correct, there is a small 'knotch' which the retaining clip locates in, if not fitted correctly then it will slip as I do not think a new gearbox will have any significant play on the gearbox control lever.

I assume you have a flexable coupling !!!

Come back for more info if needed.

Good luck
Mike





I think like everything it depends how you treat them.