Jet drive noise issue
Hello everyone ! I have recently acquired a Halmatic Pacific 24 Jet drive rib.
It has a 1994 Yanmar Diesel 6LYA-STP which was fully rebuilt in 2012 and has single figure running hours. It is coupled directly to a Castoldi 06 Jet drive. There is no gearbox between the engine and jet just a direct flexible coupling.
On the first outing after a 500 mile tow from Wales to Scotland, on increasing RPM from 3000 to 3500 there is a loud noise coming from the stern of the engine / front of the jet. There are no major vibrations however the noise becomes alarming and unbearable, It is definitely an abnormal noise.
The rib was tested prior to the journey and performed impeccably at high speed.
After a short time perhaps 5 minutes the noise dissipated and normal crusing could be resumed , however after increasing RPM above 3500 the noise returned.
I have attached a short clip of the issue , i would be most greatfull if anyone has any suggestions.
So far the following has been investigated:
- Alternator belt tension - checked and replaced with a new OEM part.
- Choked pump jet - Boat currently out of water , entire volute inspected and found to be clear.
- jet drive gearbox - oil level was slightly low and there are some signs of emulsified oil OUTSIDE of the gearbox however internal oil was relatively clean, oil was topped up and that is when the noise cleared for a while. Could be coincidense , but hydraulics ( steering and flow deflector control ) have been suggested as possible issues.
- Engine has been run to max RPM (5000) with jet clutch disengaged with no issue what so ever , noise is only evident when engine is under load.