Gearbox whine

[ianj99]

My ZF12m (Hurth HB100) whines quite loudly - louder than the engine at 1800rpm.

Are these boxes noted for gear whine?

Its a manual change but is filled with ATF - is this correct?

 

[earlybird]

I've owned a couple of boats with Hurth HBW50 boxes and not noticed any particular noise from either. The whine must be very loud to hear it above diesel engine noise.
ATF is the recommended lubricant.

 

[ianj99]

I've owned a couple of boats with Hurth HBW50 boxes and not noticed any particular noise from either. The whine must be very loud to hear it above diesel engine noise.
ATF is the recommended lubricant.

I've never heard any marine gearbox whine like this one. Its supposed to have been replaced by the previous owner a few years ago.

 

[SAMYL]

Are you sure it's not a singing prop? Does it go away at different revs?

 

[ianj99]

Are you sure it's not a singing prop? Does it go away at different revs?

A singing prop - that's a new one on me!

It varies with rpm and sounds like gear whine - not really noticeable at low rpm but above about 1200rpm, becomes very audible.
As I am finding out, the boat (bought in December) has been neglected a bit more than anticipated or led to believe so I wouldn't be surprised if this neglect is the root cause. May yet mean a strip down, like the cylinder head and anchor windlass etc etc.

 

[pampas]

Remove coupling bolts, make sure its clear and run engine in gear that it normally makes the noise . If not present the chanches are tis the prop.

 

[SAMYL]

A prop can "sing" if there is poor water flow off the trailing edge of the blades and usually happens around the revs you quote ie at 1800 or thereabouts. This happened in my boat, and with a Hurth box as well, and I tried everything to find out what it was.
The answer appeared in an article in a yottie mag and the cure was to bevel the trailing edge of the prop to a fine edge thus allowing the water flow over both surfaces to not meet again with a bang, if you follow what I mean. Apparently the poor flow causes the prop to resonate causing the loud whine, and yes it can be quite disconcerting - you think the whole drive train is failing!!

The Hurth box is quite a sturdy unit and is very unlikely to give trouble after only a couple of years even with poor maintanance. If there was oil in it then it is likely to be OK. ATF is correct.
Do as PAMPAS suggests and try the simple things first. I doubt it is the box.

 

[fisherman]

Remove coupling bolts, make sure its clear and run engine in gear that it normally makes the noise . If not present the chanches are tis the prop.

I would suggest that it may not whine unless under load. I had a whine in a PRM 500 box, I replaced it to avoid any down time. On inspection the gear teeth were very slightly chipped, maybe the result of a prop fouling (which took the box off the engine) 8000 hours earlier. I sold it to a friend, yes I did show him the teeth, he ran it for years no problem.

Problem with a Hurth is I think you have to split it to get inside, big job.

 

[Monique]

I once had a wife with a gearbox whine... I prayed to have your problem

 

[ianj99]

I would suggest that it may not whine unless under load. I had a whine in a PRM 500 box, I replaced it to avoid any down time. On inspection the gear teeth were very slightly chipped, maybe the result of a prop fouling (which took the box off the engine) 8000 hours earlier. I sold it to a friend, yes I did show him the teeth, he ran it for years no problem.

Problem with a Hurth is I think you have to split it to get inside, big job.

If it whines when disconnected from the shaft then I'd conclude it was well knackered, to use a technical term..!

I will drain and refill and also check the shaft alignment, may also fit a new flexible coupling.

Anyone know where I can obtain a workshop manual as I see that ASAP sell overhaul parts - just in case. Otherwise I will have to risk having a pile of useless bits in a heap on the floor.

 

[earlybird]

Spares, esp. the gears themselves, won't be cheap and a gearbox rebuild can be tricky with need for shimming etc.
There are currently 2 HBW100 boxes, described as brand new, on ebay.
If the 'box really is at fault, I'd be tempted to go for one of those, or from a dealer, and recover some of my cost by selling the old one.
Alternatively, you can put up with the noise !!

 

[david_bagshaw]

My ZF12m (Hurth HB100) whines quite loudly - louder than the engine at 1800rpm.

Are these boxes noted for gear whine?

Its a manual change but is filled with ATF - is this correct?

had similar when one blade of a 3 blade prop was at a different pitch.


can vouch for the singing prop fix working as well

 

[oGaryo]

different engine but had a noisey top box on my mercruiser sterndrive on purchase.. flushed it through couple of times with fresh lube and it's fine now with little or no noise to be heard