Learning experience/ with cost

[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 ?