2000 460DA Loose prop violent vibration

[kspring01075]

While cruising a violent vibration occurred and immediatly shut down engines. I thought I had hit something submerged and damaged my props. We idled back to the yard and had the boat pulled out and learned the prop was loose. The yard had just finished putting new seals on the shaft and apparently did not tighten the prop enough. The problem was when the new prop was being put on the strut moved from torquing on the prop. The mechanic informed me that the strut would have to be restuffed. Has anyone ever had this done before? Is it common and could there have been internal damage done to the area of the strut from the violent vibation I felt. Looking for actual individuals that might have gone thru something similar. Thanks

 

[osd9]

Are you sure that your 'strut' needs to be 'restuffed'? I've never hear of a strut being 'stuffed' before!!!

A lot of times, when yards put on props, it's not that they don't tighten the props nuts, it's more that they don't pre-fit the prop without the keyway and mark the shaft. They just stick the keyway in the slot, slide the prop on, tighten the nuts and 'Assume' that the prop is on the shaft all the way. Then, when you take the boat out, and everything 'relaxes' the props find a few extra '1/16ths or 1/32nds' along the shaft, and wammo....just what happened to you.

When your yard re-installs the props, make sure they pre-fit the prop on the shaft without the key.....

 

[fwebster]

The strut stuffing is really a rubber slip bearing (cutlass bearing) inside the bronze bore of the strut. The strut is bolted to the hull of the boat with 4 or 6 large bolts. The strut mounting is very substantnial; the rubber cutlass bearing is not and any excessive vibration will eat up a cutlass bearing in no time. Changing a cutlass bearing is done every day and many of us have had them changed. It takes a hydraulic or manual press, the new bearing is slipped over the shaft and used to press the old bearing out as it goes in. The old bearing is then split and removed from the shaft.

The question here is who's going to pay for the bearing replacement........bearing is about $100, the prop has to come off and be reset, and about an hour's labor involved in the bearing replacement. This is liable to be $3-$500 work with the haulout that whoever was to torque the wheel in place should be responsible for.

 

[Petep]

Yes, to both what Dom said - pre-mark the prop w/out the Keyway in
and Yes, tho what Frank said - sounds like your prop guy should get an education (or at least the bill)

 

[PMvdb395DA]

Yes, to both what Dom said - pre-mark the prop w/out the Keyway in
and Yes, tho what Frank said - sounds like your prop guy should get an education (or at least the bill)

Hello guy's,

On this moment I have my props scanned, so I have to mount them again tomorrow....
I don't know what you mean with pre mark the prop?
Can you please explain again?

Thanks Peter

 

[osd9]

Peter:

Start with valve grinding compound that you can get at most auto parts stores. Smear the compound on the saft tappered end and then install the prop on the saft without the key and rotate the prop a few turns in both directions....4 or 5 rotations should do it.....this should remove any minor burrs and give you a nice fit of the prop on the taper end of the shaft.

Make sure the prop is all the way on and then mark the shaft just behind the props hub, at the end towards the bow, with a marker. Remove the prop and clean the shaft and the inside of the prop.

Then make sure that the key fits snuggly in the shaft keyway and the prop keyway....independentaly of each other with the prop off of the shaft. If not, file or sand the key until fits nice and snuggly in both keyways and fully seats. If the key fits too loosely, get rid of it and get a new one.

Once you got that done, then place the key in the shaft keyway and put the prop on....MAKING SURE THAT THE PROP GOES ALL THE WAY TO THE MARKS YOU DID EARLIER...if the prop doesn't go all the way to the marks, remove the prop and work on the key....don't force it....no BFH here...

Once the prop is on the shaft, with the key in place, and up to your mark, then you start to put the nuts on.....that's where the real controversey starts....which nut first.....how to hold the shaft from rotating, etc, etc....

I'll stop here and let others take over....

 

[fc3]

Picking up where Dom left off.

I put my air compressor and I/R impact wrench in the back of the Navigator and brought them to the marina. Pretty easy to torque the nuts that way since the shaft never had a chance to spin.

Best regards,
Frank C

 

[kspring01075]

I want to thank Dom and Frank. This is great information and I am sure the yard mechanic installed the prop and key at the same time. They tried to convince me that I must have shifted into reverse at to high a rpm and it spun the nuts loose. I never did pay for the reapair and prop being tightend though. They were pretty good about things and had me back in the water in no time. But to my second question about the strut having a little movement caused from the vibration. They had to either repack it or restuff it is what I was told in order to make it solid and free from movement. Could any damage have been done to the core because of the vibration

Thanks for the info

 

[fwebster]

I am not sure on the 460DA, but I believe the pads for mounting the struts are solid fiberglass, as is the area in the bottom where the transducers and seacocks mount. If a strut was loose, you would see water leaking inside the boat.

Once again, the strut bore is a replacable rubber bushing called a cutlass bearing. If anything happened due to a lose prop, it was only that the rubber insert was worn or wallowed out and needed to be replaced.

Finally, my B.S. detector was screaming when I read this: " They tried to convince me that I must have shifted into reverse at to high a rpm and it spun the nuts loose. " What a load of crap..........If the prop came loose because you shifted gears too fast, then whoever installed the prop failed to torque the nut and its mating jam nut correctly.

The only way you could have had the problem you did was because the prop was not installed and torqued correctly.

 

[geriksen]

I want to thank Dom and Frank. This is great information and I am sure the yard mechanic installed the prop and key at the same time. They tried to convince me that I must have shifted into reverse at to high a rpm and it spun the nuts loose. I never did pay for the reapair and prop being tightend though. They were pretty good about things and had me back in the water in no time. But to my second question about the strut having a little movement caused from the vibration. They had to either repack it or restuff it is what I was told in order to make it solid and free from movement. Could any damage have been done to the core because of the vibration

Thanks for the info

"They tried to convince me that I must have shifted into reverse at to high a rpm and it spun the nuts loose."

Unbelievable. This is the kind of thing that gives boat yards a bad name and hurts us all.
That was just stupid to say.

We have had prop nuts come loose on us too. There really needs to be a better system.
People go to all this trouble to have their props scanned, balanced etc. and then the procedure to put it in the boat includes putting a block of wood between one blade and the bottom of the boat while you lean on a long handled wrench to tighten the nuts. I have a hard time believing that this does not bend that blade on the block slightly and knock it out of being true.
Too much pressure- you bend the blade.
Too little pressure- the nuts come loose.

The "impact" solution is good but not possible on many boats.
Outboards and Sterndrives fixed this problem with splines and castle nuts decades ago.
I don't understand why inboards still use a taper and double nuts.
That is an archaic design that doesn't work well.

 

[FireIsland1]

All is correct. After the prop is on the "thin " nut goes on first. This is securing the prop. then the " thick " nut goes on. When the thick nut is tightened it unloads and compressed the thin nut. The thick nut is now carring the load. That"s why you do not use two nuts the same size.