Disaster

[Dutch]

Well after being towed down to Alvechurch Marina and waiting 3 days for new shaft,craned out and fitted £572 pounds ,i get back into Kinver on the Staffs Worcester and the coupling bolts are all loose again and one engine mounting also loose.Now waiting for them to come out to me on Tuesday,whatr can be causing this problem

Mick

[blackrose]

Well after being towed down to Alvechurch Marina and waiting 3 days for new shaft,craned out and fitted £572 pounds ,i get back into Kinver on the Staffs Worcester and the coupling bolts are all loose again and one engine mounting also loose.Now waiting for them to come out to me on Tuesday,whatr can be causing this problem

Mick

 

I've been down into the engine 'ole tightening everything up after hearing this story. It's the second time I've heard the same thing.

 

Strange that yours have become loose again so quickly?

[Dylan]

Well after being towed down to Alvechurch Marina and waiting 3 days for new shaft,craned out and fitted £572 pounds ,i get back into Kinver on the Staffs Worcester and the coupling bolts are all loose again and one engine mounting also loose.Now waiting for them to come out to me on Tuesday,whatr can be causing this problem

Mick

When everything had been repaired, and things were still tight, did you feel any excessive vibration throughout the boat? For bolts to be coming loose so soon would suggest vibration problems and/or misalignment. Another possibility might be tired engine mounts allowing excessive movement.

 

I've been down into the engine 'ole tightening everything up after hearing this story. It's the second time I've heard the same thing.

 

Strange that yours have become loose again so quickly?

Must admit I have a habit of frequently checking tightness of things such as mounts and couplings down the engine 'ole. I keep spanners next to the engine specifically for the job. Being a tight Northener, I filed out old but excellent quality imperial ones to fit

Edited March 31, 2008 by Dylan

[magnetman]

The 'shear bolt' i was referring to was a 'shear pin' type arrangement placed in a hole drilled through the coupling and the prop shaft. The reason for it being a bolt is that if it was just a pin it'd probably fall out. Propulsion systems should be designed to take instant stopping of the propeller without damage - either the engine stops, gearbox disengages or there is a sacrificial weak point.

[magnetman]

Edited cos i heard it the first time too

Edited March 31, 2008 by magnetman

[Dutch]

After the initial repair there were no signs of any vibration at all,the engine should not be worn as the boat is just 2 years old and only 200 hours.

Mick

[stuart]

After the initial repair there were no signs of any vibration at all,the engine should not be worn as the boat is just 2 years old and only 200 hours.

Mick

 

Did they check the prop for damage? Perhaps a bent blade is causing vibration through the shaft to the engine?

 

Is there any flexible prop mounting? R&D coupling/aquadrive/python unit or similar?

[Dutch]

Did they check the prop for damage? Perhaps a bent blade is causing vibration through the shaft to the engine?

 

Is there any flexible prop mounting? R&D coupling/aquadrive/python unit or similar?

 

Yes it is an R&D coupling,it is the bolts through this that come loose.

Mick

[blackrose]

The 'shear bolt' i was referring to was a 'shear pin' type arrangement placed in a hole drilled through the coupling and the prop shaft. The reason for it being a bolt is that if it was just a pin it'd probably fall out. Propulsion systems should be designed to take instant stopping of the propeller without damage - either the engine stops, gearbox disengages or there is a sacrificial weak point.

 

My coupling 'grips' the shaft rather than being directly connected through a hole. In this case I guess a shear bolt wouldn't do anything?

[magnetman]

I guess not, but maybe the coupling itself would slip around the shaft?

[blackrose]

I guess not, but maybe the coupling itself would slip around the shaft?

 

Perhaps that's what it's supposed to do? Now I'm wondering if I should have tightened the bolts so much?

[John Bean]

Would Loctite help??

 

John

[Dylan]

Yes it is an R&D coupling,it is the bolts through this that come loose.

Mick

I too have an Rand D on this boat, and one on the previous. I am surprised that these are coming loose, as I have not experienced this. i had to take the R and D off the previous boat for different reasons, and they were swines to undo. Gut feeling is that something is misaligned. Maybe speak to R and D?

 

http://www.randdmarine.com/contactus.asp

 

Alignment procedure:

 

http://www.randdmarine.com/flexiblescinst.asp

Edited April 1, 2008 by Dylan

[RupertG]

Out of interest, what would happen with a stalled prop and an electric motor? Drive current would go up, I guess, until some sort of protection kicked in - result, nothing damaged?

 

R

[arlow11]

you could mark your nuts ie a drop of paint at 12 oclock,not the time..........although doing it at 12 could balance the chi

[blackrose]

I guess not, but maybe the coupling itself would slip around the shaft?

 

My chandler reckons the coupling isn't designed to slip around the shaft in the event of the prop being stopped. He says the clutch in the gearbox would give. Does a PRM 150 hydraulic box have a clutch? I thought the drive was always engaged - even in neutral, and it was just the direction of oil flow that determined whether it was in forward or astern.