45C cracked shaft

[elpescador47]

All the advice is appreciated. I don't know much about prop shafts, but I'm learning. Thank you.

I'm going to pass on the shaft in a box and have the shop fabricate a new one for me.

What the guys at Wilmington Iron Works told me is very in line with your thoughts. They told me they were going to make it out of AQ22HS (I may have left the "HS" off on my prior post). At this point, if the starboard shaft checks out, I don't think I'm going to replace it. I will have the shop make longer keys. I'll ask them about the keyway not being "spooned".

The guys at the shop also wanted to calculate the safety factor for the shafts--I just need to get the gear ratio for the transmissions, which I will do next time I'm down on the boat.

I'll post updates.

Please let me know if you have any other thoughts or advice!

[elpescador47]

Updates and more questions:

The shaft:
Per the shaft shop, the starboard shaft is bent (at the engine end),but not cracked. The shop can straighten it.

They also calculated my safety factor and found it to be 3.49, and if I had 2.25" shafts my safety factor would be a more acceptable 4.98. They did this based on the following information:

HP: 550
Shaft diameter: 2"
Gear ratio: 2:1
Max RPM: 2200
Shaft material: AQ22HS

The props were re-sized in 2004, way before I bought the boat. I was told that they had been resized to go easier on the engine. I have a vague understanding of what this means. Prop measurements are as follows:
Diameter: 29
Pitch: 30
Blades: 4

I've always thought that Hatteras overbuilt everything. I would imagine that it's an expensive decision to change shaft size. Aside from the crack in the port shaft (which is likely multi-factorial in etiology), they've done pretty well for a long time. Have people had trouble with their shafts? Is upsizing the propeller shafts from stock something people do (aside from during a re-power)? My current plan is to have a new shaft fabricated (AQ22HS) for the port shaft, which is cracked, and have them straighten my starboard shaft.

Cutlass bearings:
While the starboard shaft was out (now for the second time in a week) I had a chance to look at the cutlass bearings myself. When the shaft had come out the first time it had been put back in before I had a chance to go back to the boat. Both starboard cutlass bearings, and in particular the intermediary strut cutlass bearing, looked worn out (pictures attached) and need of replacement. Given my inexperience in evaluating the cutlass bearings I asked the yard to take a second look. Before they could get back to me, I told them to just change them out.

I was concerned because the yard rolled the shaft and told me they checked the cutlass bearings. They didn't think the shaft was bent and told me the cutlass bearings were fine, which is why I didn't send the shaft to the shaft shop when they pulled it out the first time. I discussed my concerns with the yard. They said that rolling the shaft isn't as sensitive as what the prop shop does to determine whether or not a shaft is bent (which I understand). They said that the shaft was not loose in the cutlass bearing, so they thought it was fine. I understand checking the cutlass bearings that way if you're not removing the shaft, but with the shaft out I would think that a visual inspection should be done, and wear to the degree that my boat had should be identified. If I'm off here, please let me know. I kind of read them that riot act over this.

Thanks again for your advice IMG_0615.jpgIMG_0645.jpgand comments.

[jim rosenthal]

It sounds like perhaps you should replace the cutlass bearings in the stern tubes and struts; do you have the option of going with thin wall bearings so you can go up on the shaft size? You could probably gain another 0.25" of shaft thickness if you did that. Mind you, the bearings would not last as long, from what I understand, but in our sorts of uses that doesn't seem to be a big concern.

I think you are going the right way with the new shaft. As Pascal said, this is not a place to skimp.

[Cricket]

Wouldn't be worried about the shaft size, there's a ton of those boats on the water with the same set up.
The shaft safety calculation really needs to be done using the metal hardness numbers of the actual shaft batch, there's a huge range batch to batch.
We have 800hp CATS with 1.5 to 1 gears using 2" shafts. Over 5,000 hrs of service with 1 cracked shaft which was caught during a wheel change luckily. We're not sure but why it cracked. but we did have a loose wheel which may have caused it.
Make sure the keyways are spooned and also that there's a small radius in the bottom of the key way and not a hard 90.

Your WOT RPM is low? Should be 2,300 or 2,350???

[kelpy]

I would always change out the bearings when a shaft is pulled. Makes for an easy job as long as the yard has a puller/ installer press tool. Is the shaft scored up where it was riding on trashed bearing?

[elpescador47]

Just a brief thank you and update to all of those who responded to my question last year:

I replaced the port shaft with a brand new shaft (same size: 2" AQ22HS). Re-balanced both props. New cutlass bearings. New shaft seals. Spent a lot of money and learned a lot.

I have run the boat a lot (for me) since then, and taken it farther and farther offshore.

The engines run smoother and hit full rpm without vibration.

I have a lot more confidence having gone with the new shaft than I would have had I opted for used/questionable.

The old shaft and an old banged up prop is at home waiting to get turned into a lawn sculpture.

On a related note, Wilmington Propeller and Wilmington Iron Works are phenomenal businesses: good, honest people who do good work. I can't speak highly enough of them.

Again, thanks to everyone who responded to me, and all of you who post pearls of wisdom on this forum.

[Photolomy]

I may be a little cheap sometimes but not when it comes to wheels whether on the road or in the water. On the road I look for the softest possible rubber to get max grip. In the water, trying to save a few bucks on shafts is a gamble too. Have a good prop shop donthe calculatuons to see which shaft material will work for your boat. Maybe standard AQ22 will be fine or even lower. Maybe Hatteras can confirm what material they used back then

By the time you pay for the labor, etc the extra $ for the best possible SS stock makes little difference

Raising a 40” wheel from 22’ without tanks after a two day search isn’t something I want to do again

Did you return for the prop, or get it while you were there?

[jim rosenthal]

Based on what he said about doing it without tanks, I'm going to guess that he did it when it broke off. Having lost an anchor, marked it on GPS immediately, and never finding it, I think when you go back you are likely to miss whatever went down to the bottom.

That's quite a dive on breath-holding, Pascal. Or did you have a hookah rig with you?

[jim rosenthal]

Just a brief thank you and update to all of those who responded to my question last year:

I replaced the port shaft with a brand new shaft (same size: 2" AQ22HS). Re-balanced both props. New cutlass bearings. New shaft seals. Spent a lot of money and learned a lot.

I have run the boat a lot (for me) since then, and taken it farther and farther offshore.

The engines run smoother and hit full rpm without vibration.

I have a lot more confidence having gone with the new shaft than I would have had I opted for used/questionable.

The old shaft and an old banged up prop is at home waiting to get turned into a lawn sculpture.

On a related note, Wilmington Propeller and Wilmington Iron Works are phenomenal businesses: good, honest people who do good work. I can't speak highly enough of them.

Again, thanks to everyone who responded to me, and all of you who post pearls of wisdom on this forum.

I'm still thinking about that shaft that the guy had for sale. Now that you have your boat squared away, maybe you should see what you can find out about that one. If it's Aq22, it might be worth buying.

[Pascal]

It was too rough that day to stop and look. So we continued the trip and stopped a week later on the way back. Took three days to find it as on the first two days visibility wasn’t great. Spent about 5 hours each day with naomi towing me with the tender.. third day was dead calm so we did passes with the boat and spotted it on on the bottom on the 3 rd pass. GPS tracks showed I passed real close the day before.

No hooka. Free diving. Naomi is a real good swimmer so we took turn going down tying a line. Difficult because by the time you get down to 20’ you don’t have much time.

Used an aft deck winch to bring it close to the surface then hauled it up with the davit.

I kept the broken shaft piece as a souvenir