Learning experience/ with cost

[Tim Powell]

today was a cluster mess.. I found my lost prop had to put a reward on the thing the guys at the mariner found it. Cheaper than purching a new one or two. +++++++ The shaft broke it was 2 1/2 inch thick. The new shaft arrived yesterday indtalled the new shaft bolted it to the coupler and off we went to slide the prop on. The shaft was made to hatteras specks as to what came on the boat got the speck sheet from Hatteras. The company that turned the shaft said he should check the prop to the shaft. (past experience told him mis fit props broke shafts) Well have at it and he did the prop was off that was what caused the shaft to brake. With that in mind nothing to do but check the other shaft and prop. After removing the prop he put a red bye on the shaft and a crack in the exact same place as the other broke. After a bunch of bull and talking nothing to do but purchase a new shaft. My point

When purching a boat eaven with all you know and the best survaror in the business will miss that .
Probley will not eaven think about checking it it cost 2 shafts 8000 plus hall out 300 plus labor to remove and install 2 shafts and fus cut the props to properly match 3000
total cost about a 12000 hit .

Outcome slick and smooth .There was a small vibration at about 1600 to 1800 not enough to really worry about if you got one find the problem if you are thinking about purching. Do not just sluff it off Tim

 

[Boatsb]

today was a cluster mess.. I found my lost prop had to put a reward on the thing the guys at the mariner found it. Cheaper than purching a new one or two. +++++++ The shaft broke it was 2 1/2 inch thick. The new shaft arrived yesterday indtalled the new shaft bolted it to the coupler and off we went to slide the prop on. The shaft was made to hatteras specks as to what came on the boat got the speck sheet from Hatteras. The company that turned the shaft said he should check the prop to the shaft. (past experience told him mis fit props broke shafts) Well have at it and he did the prop was off that was what caused the shaft to brake. With that in mind nothing to do but check the other shaft and prop. After removing the prop he put a red bye on the shaft and a crack in the exact same place as the other broke. After a bunch of bull and talking nothing to do but purchase a new shaft. My point

When purching a boat eaven with all you know and the best survaror in the business will miss that .
Probley will not eaven think about checking it it cost 2 shafts 8000 plus hall out 300 plus labor to remove and install 2 shafts and fus cut the props to properly match 3000
total cost about a 12000 hit .

Outcome slick and smooth .There was a small vibration at about 1600 to 1800 not enough to really worry about if you got one find the problem if you are thinking about purching. Do not just sluff it off Tim

Welcome back to boat ownership.

 

[davidwigler]

What exactly was wrong with the prop to shaft fit? I've never heard of this problem.

 

[34Hatt]

What exactly was wrong with the prop to shaft fit? I've never heard of this problem.

Lapping the prop to shaft and checking the fit it has been mention here many many times and is all over boat diesel Tony has a Tip section on it good read. I lap mine every time they come off regardless of how many times prior they have been done. Also you need to check the key way fit and make sure its not hanging up on it.

 

[Bob Bradley]

I lost a prop the same way. It was an expensive lesson.

I had both props removed and reinstalled by a diver without pulling the boat. While being reinstalled, they got hung on the key apparently, and never fully seated. A year later one broke off just in front of the prop. I checked the other and it too was cracked and would have failed.

Bottom line is this: Always haul to do the props. Always fit the props with lapping compound. Use coarse compound first. Apply it liberally, snug the nut slightly, then spin the prop on the taper. As you spin it, it gets looser. Tighten the nut and spin it some more. A lot more. Take it apart, clean it up, then apply fine lapping compound - again, liberally. Repeat the process.

Finally, install the prop. Remember, the key does not carry the prop. It only aligns it. The prop must be fully pressed against the tapered shaft. Also, use the big nut to press the prop on, then once on, remove the big nut and put the smaller nut onto the threads and tighten. Finally, put the big nut on last and tighten. Don't forget to put in a new cotter pin.

 

[bigbill]

i agree with bob about how to lap the prop. when i'm done lapping the prop, i mark the shaft at the fwd end of the prop, then install the key, and make sure the prop makes it all the way on the shaft up to the mark that i made without the key. this insures that the prop isn't binding on the key.

 

[krush]

blue check?

 

[Jasper]

today was a cluster mess.. I found my lost prop had to put a reward on the thing the guys at the mariner found it. Cheaper than purching a new one or two. +++++++ The shaft broke it was 2 1/2 inch thick. The new shaft arrived yesterday indtalled the new shaft bolted it to the coupler and off we went to slide the prop on. The shaft was made to hatteras specks as to what came on the boat got the speck sheet from Hatteras. The company that turned the shaft said he should check the prop to the shaft. (past experience told him mis fit props broke shafts) Well have at it and he did the prop was off that was what caused the shaft to brake. With that in mind nothing to do but check the other shaft and prop. After removing the prop he put a red bye on the shaft and a crack in the exact same place as the other broke. After a bunch of bull and talking nothing to do but purchase a new shaft. My point

When purching a boat eaven with all you know and the best survaror in the business will miss that .
Probley will not eaven think about checking it it cost 2 shafts 8000 plus hall out 300 plus labor to remove and install 2 shafts and fus cut the props to properly match 3000
total cost about a 12000 hit .

Outcome slick and smooth .There was a small vibration at about 1600 to 1800 not enough to really worry about if you got one find the problem if you are thinking about purching. Do not just sluff it off Tim

Sorry to hear about this Tim. Hard way to start when you have done all that research and careful surveying. Let's hope it's a long while before another major problem/cost shows up.
Good luck Mate!
George

 

[Avenger]

blue check?

No, no, no!

That would suggest that parts can be made so they can be assembled without hand fitting.

A concept that hasn't been invented yet.

 

[Tim Powell]

I lost a prop the same way. It was an expensive lesson.

I had both props removed and reinstalled by a diver without pulling the boat. While being reinstalled, they got hung on the key apparently, and never fully seated. A year later one broke off just in front of the prop. I checked the other and it too was cracked and would have failed.

Bottom line is this: Always haul to do the props. Always fit the props with lapping compound. Use coarse compound first. Apply it liberally, snug the nut slightly, then spin the prop on the taper. As you spin it, it gets looser. Tighten the nut and spin it some more. A lot more. Take it apart, clean it up, then apply fine lapping compound - again, liberally. Repeat the process.

Finally, install the prop. Remember, the key does not carry the prop. It only aligns it. The prop must be fully pressed against the tapered shaft. Also, use the big nut to press the prop on, then once on, remove the big nut and put the smaller nut onto the threads and tighten. Finally, put the big nut on last and tighten. Don't forget to put in a new cotter pin.

Bob I must agree never use a diver, After checking i found that a diver did this work in florida befor i purchased the boat.
A small vibration caused the owner to pull the props and have them ballanced, Diver did the work...

 

[Bob Bradley]

Yup.

At least it sounds like you got your prop back. I lost mine at 17kts running in 40fow. And yes, it did make a big bang as it departed. Also cut a major slice in the bottom. Thank God its a Hatt; a lesser hull would have been breached.

I had a diver do my old Chris (gas engine, 1-1/4" shaft) many times with no problem. I did find a prop loose once or twice. I guess the stresses of a much bigger power plant on a much bigger boat and running gear are substantially different. Before all was said and done with new prop, two new stub shafts (got them free from a generous site member, but paid big bucks to have them reconditioned), and a couple haulings and propscans to get everything perfect, I figure that mistake cost me north of $6k.

 

[Diesel]

Tim- I dont think you could have forseen that problem. Hopefully the boat bucks stay in your wallet for a while. Hopefully when we die it will be with a big smile on our face from all the enjoyment our Hatteras' brought us. Enjoy your boat...life is good.

 

[saltshaker]

I feel your pain Tim. My governor failure cost me 25K. But that's part of the game. I think we are both still in great shape considering what we've got and what we paid for them.

 

[krush]

No, no, no!

That would suggest that parts can be made so they can be assembled without hand fitting.

A concept that hasn't been invented yet.

So what's the point of the key way then? To center the bores?

 

[jim rosenthal]

I'd like to know this, too. Does the force to turn the prop come through the key? Or once the prop is lapped on, it's on so tight that the shaft can turn it without slipping inside the prop bore? Hard to imagine, with all that torque.

 

[Avenger]

The key does not drive the prop. All the load is carried on the taper. Basically it's like a wedge which is why it's so difficult to remove once it's seated. I work with tapered drive couplings all the time and a properly machined shaft and bore should fit together and work correctly without hand fitting. The only purpose I can see for lapping, or as krush suggested a "blue test" is to verify that the components are in fact mated properly. However, once that's proven I can only see opportunities to foul things up by repeatedly fiddling with them.

On the coupling end the key would be for alignment since the coupling face is supposed to be trued on a lathe while mounted on the shaft. Hence realigning it in a different position could potentially cause a problem. Props OTOH, are not "trued" on the shaft so there's no need for indexing. The only purpose I can see for the key on the prop end is to keep the prop from spinning while you're torquing the nut. If anybody knows another reason I'd like to hear it. Perhaps there's concern about bending a shaft if it's held in some other place while torquing but since we don't use a spanner to hold the prop that potential exists anyway. Or maybe "we've always done it this way." But frankly, if I ever have shafts made I'm going keyless on the prop end. Keyways are just a potential failure point and a key is an opportunity to put a prop on cockeyed.

 

[Avenger]

Here's a case in point: My 3208 injection pump. All the drive force and pump to engine timing is handled by a tapered drive. If it slips it goes out of time and runs lousy if at all.

No key.... no keyway.

 

[bigbill]

scrod, the reason for lapping is that when a prop is repaired with a torch, there is the chance that the heat may distort the bore

 

[krush]

What's the point of lapping with out some type of verification...aka blue check? If it's really messed up, you ain't going to fix it with lapping compound anyway. And blue checking can have u chasing your tail because it either touches or doesn't...you can't see how far away it is.

One could just leave the key out at the prop end. Then no worries! Keys are used to transmit power all the time, but it usually is on a straight (read non-tapered) shaft.

 

[lumina]

Hi All,

Tim....Oooouch that's a big one !!

Jack......Oooooooouuuuuccccccchhhhhhhh !!!!! Holey Moley !! Isn't that almost the cost of a re-build ?

Tim,, As Jack and others have said, have confidence in your research, you have a beautiful boat, well cared for, and it's not something you could have foreseen, and unfortunately we've all been subject to Murphy's law in our passion for our classic Hatts.......

Bill, you said "the reason for lapping is that when a prop is repaired with a torch, there is the chance that the heat may distort the bore""....so does the lapping compensate for the distortion and the key then forces alignment or acts as a lock ?