noise from gearbox while sailing

[jarwin]

Good morning.
We have a 1997 Beneteau 36cc with Volvo Penta 2040 diesel inboard and fixed 15" propellor and live and sail in the Middle East. At 7 knots a loud 'droning' sound came from the gearbox which felt very hot. The sound stopped when our speed was below 7 knots. This has not happened before.
We recently fitted a new prop shaft seal and cutlass bearing and the shaft is now stiffer to rotate by hand than before. We have now greased and vented the seal and will, wind permitting, sail again this weekend. Any thoughts please? Could it be the gearbox bearings? It is advisable to fit a prop shaft brake?
Best regards
Rosemary and Jim Winter.

 

[Mike Holibar]

Try putting the transmission in reverse when sailing. This should prevent the shaft rotating. If you still get the noise at 7 knots then it could be some resonance from water travelling over the prop blades - the singing propeller trick.
If the shaft is rotating the new cutlass bearing may be binding up. Or, if the gearbox is in ahead position, the shaft willl rotate but wear the cone clutch as it slips. This would generate heat and possibly noise as you describe. If the transmission oil looks dirty (black) that would indicate that this is the problem. Change the oil and engage reverse when sailing to lock the prop. Good luck,

 

[jarwin3]

Try putting the transmission in reverse when sailing. This should prevent the shaft rotating. If you still get the noise at 7 knots then it could be some resonance from water travelling over the prop blades - the singing propeller trick.
If the shaft is rotating the new cutlass bearing may be binding up. Or, if the gearbox is in ahead position, the shaft willl rotate but wear the cone clutch as it slips. This would generate heat and possibly noise as you describe. If the transmission oil looks dirty (black) that would indicate that this is the problem. Change the oil and engage reverse when sailing to lock the prop. Good luck,

Thanks Mike
Volvo Penta handbook says NOT to engage reverse gear to stop shaft rotating but to fix a shaft brake. We always sail with shaft rotating. Gearbox oil is clear. We'll see if problem re-occurs this weekend.
Thanks again
Rosemary and Jim Winter

 

[Stu Jackson]

It is NOT the engine that determines gear positions that are acceptable it is the transmission. Of course, the Volvo Penta instructions may cover both the engine and the transmission.

Never listen to gear position advice unless they ask what transmission you have.

Yes, shaft brakes are available. Why not Google them or check www.marinedieseldirect.com (a very good engine supplier's website who may or may not have them) for some leads.

What you're really asking is: "Where can I get a shaft brake?"