help diagnose hurth gearbox problem

[granche1]

Hi Everyone.


I am hoping that a gearbox expert might be able to help me diagnose what might be going on with my Hurth 150.



After the gearbox has sat in neutral for several days (weeks?), when I shift it into either forward or reverse there is a hellish amount of grinding noises that bellow forth from the engine compartment. This god awful racket seems to clear up and go away after 5-10 seconds at which point everything seems to work fine.



I have committed several Hurth no nos in my 10 years of ownership. I have left the gearbox in forward while sailing across most of the pacific, I have let the gearbox sit for year long periods without filling it full of ATF, and I have discovered it at one point seeming to lack any ATF at all in it. Having a few months ago filled it properly, it does not seem to be loosing ATF at any great rate at least.



Any idea about why the thing grinds and then seems to clear up?


Much appreciated.


Grant Gardner
s/v Viandante
Pohnpei, Micronesia

[granche1]

Does anyone have any idea what could be going on here? Damper plate? I manged to sail / motor a couple thousand more miles to Palau since the problem began but faced with a 6 day motor to the philippines i would like to wrap my head around this before i destry something.

Grant

[Uncle Bob]

Originally Posted by granche1

Does anyone have any idea what could be going on here? Damper plate? I manged to sail / motor a couple thousand more miles to Palau since the problem began but faced with a 6 day motor to the philippines i would like to wrap my head around this before i destry something.

Grant

Hi, does the noise occur when the engine is running with the gearbox in neutral? or does it only occur when the box is engaged. If the noise is there with the engine running but box in neutral then I would suggest that the suspect is the damper plate, if not but only when actually in gear then the gearbox is more likely the suspect.
Either way it should only take you a few hours to part the engine and gearbox and check the damper plate.
Good luck.

[skipperpete]

Originally Posted by granche1

Does anyone have any idea what could be going on here? Damper plate? I manged to sail / motor a couple thousand more miles to Palau since the problem began but faced with a 6 day motor to the philippines i would like to wrap my head around this before i destry something.



Grant

Hi Grant, there is a problem that arises with propeller shafts on boats that sit for various periods of time without shaft rotation. A sort of fine encrustation of either coral or some sort of calcium builds up on the shaft between the flutes of the cutless bearing where there is no contact with the rubber. It can be very thick, as much as .5mm and makes a hell of a noise at first but finally either smooths out or flakes off and sounds very much like a gearbox internal issue until it clears. in severe cases it will wear the cutless dramatically but this is on boats that have been inactive for a year or so. Easy to fix, undo the coupling , slide back the shaft and gently remove it. If this is what the problem is on your boat the non rotation/ standing time is suspiciously short for a build up.
Good luck , hope it's not the gearbox.

[granche1]

Originally Posted by Uncle Bob

Hi, does the noise occur when the engine is running with the gearbox in neutral? or does it only occur when the box is engaged. If the noise is there with the engine running but box in neutral then I would suggest that the suspect is the damper plate, if not but only when actually in gear then the gearbox is more likely the suspect.
Either way it should only take you a few hours to part the engine and gearbox and check the damper plate.
Good luck.

Thanks Bob.
The noise only occurs when i put the engine into forward or reverse and after the motor has not been put into gear for a week or so. I guess that rules out the damper plate? When i do open it up, what would i be looking for to identfy a problem with a damper plate?

Grant

[granche1]

Originally Posted by skipperpete

Hi Grant, there is a problem that arises with propeller shafts on boats that sit for various periods of time without shaft rotation. A sort of fine encrustation of either coral or some sort of calcium builds up on the shaft between the flutes of the cutless bearing where there is no contact with the rubber. It can be very thick, as much as .5mm and makes a hell of a noise at first but finally either smooths out or flakes off and sounds very much like a gearbox internal issue until it clears. in severe cases it will wear the cutless dramatically but this is on boats that have been inactive for a year or so. Easy to fix, undo the coupling , slide back the shaft and gently remove it. If this is what the problem is on your boat the non rotation/ standing time is suspiciously short for a build up.
Good luck , hope it's not the gearbox.

Skipperpete,

That is very interesting. I do have a bit of calcium on the shaft inboard of the packing nut and my prop and bottom were bascly a coral reef after leaving the boat in majuro for a year. I also have a good amount of wiggle in my shaft so plenty of room for coral to grow in there. I know the cutless needs to be replaced hence the upcoming trip to PI. I would really love for this to be the problem. Amazing if the stuff really grows that fast.

Grant

[GordMay]

Hurth ‘HBW’ Manual
➥ http://www.wbryant.com/temp/hurth_manual.pdf