david_bagshaw
Well-known member
My suggestion would be to have the prop refurbished, with particular attention the forward facing, edge, which can set off singing noise, along with having the blades checked for equal pitch.
Should I remove my flexible shaft coupling?
- Thread starter Hoist
- Start date
Hoist
Active member
Thanks everybody for your replys and advice but I think I have found the culprit in an unlikely place.
The other evening I was preparing the shaft to come out for changing the worn cutlass bearing. I removed the blades from the prop and loosened the locking grub screw for the propeller nut.
My friend was coming to give me a hand in the morning as we are also doing an engine swap but that evening I did not have the 21mm socket required for taking the nut so I called him to say "bring a 21mm"
Upon arrival we looked over the boat and he said "so you got the prop nut loose then?"
Having not touched it I was very confused. I said "no I only took the grub screw out."
Basically, the propeller has been locked onto the taper for the last 5 years by the little locking grub screw. I think the seriously cold weather we have been having overnight also made the prop loosen itself off the taper because it was solid the night before.
the nut was still solid however, 21mm rounded, 20mm rounded, 19mm rounded and then the 18mm whacked to within an inch of its life by thor and the big breaker bar managed to get it off.
Looking at the prop hub and the nut you can see that both sides that should have been mated are dirty.
The end of the shaft has been sticking through past the mating face of the prop hub
We checked this with a very near and its 3-4mm proud
Not ideal but we think its due to the small hub size of the Gori Race prop. When it was originally bored they took the old prop to match it and there is no rocking when the hub is on the shaft so we are 99% sure its the right taper.
checking the depth
Roughly 31.9mm from the end of the shaft to the prop hub
28.8mm of thread depth on the shaft
Solution is fairly simple. We are having a prop nut machined with a counterbore of 6mm to allow for the discrepancy.
I hope that with the prop fully onto the taper and aligned properly onto the shaft that it cures the riddle. ?
If it doesn't I'm putting in a sail drive ?
The other evening I was preparing the shaft to come out for changing the worn cutlass bearing. I removed the blades from the prop and loosened the locking grub screw for the propeller nut.
My friend was coming to give me a hand in the morning as we are also doing an engine swap but that evening I did not have the 21mm socket required for taking the nut so I called him to say "bring a 21mm"
Upon arrival we looked over the boat and he said "so you got the prop nut loose then?"
Having not touched it I was very confused. I said "no I only took the grub screw out."
Basically, the propeller has been locked onto the taper for the last 5 years by the little locking grub screw. I think the seriously cold weather we have been having overnight also made the prop loosen itself off the taper because it was solid the night before.
the nut was still solid however, 21mm rounded, 20mm rounded, 19mm rounded and then the 18mm whacked to within an inch of its life by thor and the big breaker bar managed to get it off.
Looking at the prop hub and the nut you can see that both sides that should have been mated are dirty.
The end of the shaft has been sticking through past the mating face of the prop hub
We checked this with a very near and its 3-4mm proud
Not ideal but we think its due to the small hub size of the Gori Race prop. When it was originally bored they took the old prop to match it and there is no rocking when the hub is on the shaft so we are 99% sure its the right taper.
checking the depth
Roughly 31.9mm from the end of the shaft to the prop hub28.8mm of thread depth on the shaftSolution is fairly simple. We are having a prop nut machined with a counterbore of 6mm to allow for the discrepancy.
I hope that with the prop fully onto the taper and aligned properly onto the shaft that it cures the riddle. ?
If it doesn't I'm putting in a sail drive ?
Attachments
Poey50
Well-known member
Good feedback. I hope your gearbox is fine after all that whacking.
Hoist
Active member
Sadly there was no other way to do it.
We had to weigh it all up, the gori race prop was £1500 5 years ago, the gearbox is 28 years old and about a grand for a new one last time I checked and its far easier to get.
Fingers crossed,
penfold
Well-known member
Yikes. Did it vibrate prior to the Gori being fitted?
Hoist
Active member
No idea as it was one of the first things we did when we got the boat, new cutlass bearing, fixed prop off.
I always thought it was the old engine mounts or the alignment
utterly amazes me that it never moved.
Never had a reason to take the prop off in the last 5 years but there was no reason to ever doubt it was loose.
Everything was tight so you just assume it fits.
penfold
Well-known member
Given it's been moving around for 5 years best to check there's no wear in either taper with some engineer's blue.
Topcat47
Well-known member
IF you're going to replace the Gori Prop, check the fit of the blades and the pins. It's possible that the pins/bushes on the prop have begun to wear and that's the source of the noise. You have the prop off so it ought to be fairly straightforward. 5 years isn't a particularly long life for one but the vibration is a good excuse to check it out, while it's off and the boat's out of the water. It's be a shame to do all this work and still not cure the problem. Straightening my shaft and re-balancing my own three bladed fixed prop did wonders for my boat.