ZF gearbox on Cummins QSB 5..9 and vee drives - strange whining noise.

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driver0606

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Hello,

I have a 2006 Azimut 43 with twin Cummins QSBY 5.9 engines and ZF gearboxes with vee drives. The port engine has a strange high pitched whine that comes in only at idle (650 rev/min) and at about 800 to 900 rev/min and only when in forward gear. It disappears at all other speeds it is not especially loud and could almost be explained as normal, but does not occur with the other engine. The noise has a slight pulsation as if it is connected with the propellor shaft and does not occur in neutral. The shaft alignment is not far out, but impossible to get spot on with the engine being rubber mounted.

Any ideas, please?
 
driver0606 said:
Hello,

I have a 2006 Azimut 43 with twin Cummins QSBY 5.9 engines and ZF gearboxes with vee drives. The port engine has a strange high pitched whine that comes in only at idle (650 rev/min) and at about 800 to 900 rev/min and only when in forward gear. It disappears at all other speeds it is not especially loud and could almost be explained as normal, but does not occur with the other engine. The noise has a slight pulsation as if it is connected with the propellor shaft and does not occur in neutral. The shaft alignment is not far out, but impossible to get spot on with the engine being rubber mounted.

Any ideas, please?
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Right, many years back a similar if not the same problem occurred on a boat I knew of, Cummins engineers swapped the gearboxes so I'd enquire with Cummins uk about this as I'd guess there may be a fix at there cost. From memory it was an issue with the drive coupling on the flywheel .
 
Sometimes a prop can sing it's usually at lower revs and can be quite annoying. Ibelieve it's something to do with the shape of the leading edge of the prop causing a disturbance in the water that resonates up the shaft and through the hull?
 
Relax.A said:
Sometimes a prop can sing it's usually at lower revs and can be quite annoying. Ibelieve it's something to do with the shape of the leading edge of the prop causing a disturbance in the water that resonates up the shaft and through the hull?
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Agree. I have the same singing noise at 800 and 1500. I thought it was my zf box but had it checked out and it was fine, the guy said the leading edge of the prop blades need to be rounded off. I just live with it for now.
 
Re: Update. ZF gearbox on Cummins QSB 5..9 and vee drives - strange whining noise.

Thank you very much for your comments. I have now discovered that the water supplies to both HSS seals were completely blocked. They are now cleared of course. I thought this was checked when new seals were fitted last year, but it seems not. There is no apparent damage to the seals and no noise from the starboard side, so I guess it could still be propeller noise.
I am still waiting to hear from Cummins about the possible coupling problem. Does a noise from that or from the HSS seals come in only at certain revs, or is it always present?
 
volvopaul said:
Right, many years back a similar if not the same problem occurred on a boat I knew of, Cummins engineers swapped the gearboxes so I'd enquire with Cummins uk about this as I'd gualless there may be a fix at there cost. From memory it was an issue with the drive coupling on the flywheel .
Click to expand...

Paul, there was an issue with B Series and and certain ZF transmissions, 63 springs mind. The gears chattered at idle particularly if engine had P7100 pump with RSV governor with lower idle speed. Torsional compatibility issue, fix was real simple, Cummins paid to campaign engines with heavier flywheel which was a total fix.

The only issue with QSB's that I am aware of is a piecing whistle which was difficult to solve as it appeared to be utterly random. Turned out that the stainless steel turbo gasket had which had slightly too much tolerance allowing on occasions for it to protrude slightly into the exhaust gas flow and boy could that piece of gasket cause a howl....
 
Hello Latestarter1, nice to hear from you. Guess I will just monitor the noise and the HSS seals and do a big service over the winter. Any suggestions for buying Cummins parts economically in the States, please?
 
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