Stern tube A25

[Dieselram94]

The shaft is 1.25”
I’m guessing it is that big because I have a Perkins 4.108 (50hp)

Interesting. If it was metric then 1.25" = 31.75 mm. Sounds like a bit oversize 30mm shaft. Probably not original to the boat? Or was it SAE to begin with? Otherwise ditto what WillieC said. A 25 mm shaft would be 0.984", and a 1" shaft would be 25.4mm.

Pretty sure shaft is not original. I have a brand new Albin 30mm cutless but it’s too small. It currently has a new 1.25” cutless in it.

[WillieC]

If it is salt build up, it should scrape off and reveal nice and shiny bronze underneath. If it keeps going, deeper and deeper, then it would seem to be worse than salt.

So I am trying to wrap my head all around this. Sounds like an inch and a quarter shaft, clearly not original. So somebody replaced the original shaft, of whatever material, with an SAE bronze shaft. Wow. Maybe it was just laying around, like my mystical sailboat shaft. OK...So, now the cutlass had to be modified to fit. Not too tough using a stock 30mm and a little working to get it to fit the 1.25". So far so good. Now what taper is on it? Your accessibility may be different, but going to all that trouble to install an SAE shaft, I would certainly want an SAE taper on it. I am getting off topic. Sorry.
Poke around and see how bad the corrosion is. I am running my 36 HP VP engine at no more than 1000rpm at the shaft (2000 at the engine). It ain't perfect, having checked it on the lathe bed. I can live with it. With more HP and RPMs it might be a very different story.

I am not familiar with the bolt on shaft log you describe, but there are numerous ways to fix these issues. If I had to replace the log, I would certainly figure out how to convert to a standard cutlass set up. You've got to hand it to the Swedes though, with the original cutlass-in-a-ball arrangement that self-centers. Stefan, Albinmotors, offers a few non-standard cutlasses, 1" for sure, in addition to the 25mm and 30mm. Not sure about 1.25". I mention this only because there are a pile of knee-bone connected to the shin-bone issues when you start fooling around with bigger engines/shafts/couplings/shaftseals/ cutli/props AND now shaft log.

Way back when, if you have read any of my earlier posts, before I ever worked on the engine, I did replace a couple shot mounts and figured out how to install another cutlass bearing to serve as midshaft (sort of) support up at the top of the shaft log. Seven feet on a 30mm shaft with support only at both ends seemed a bit excessive. Finding something that would fit inside the tube and still fit the shaft was tricky, but I came up with an all rubber cutlass bearing for Beneteau sailboats. It was just a little sloppy in the tube, but a couple dabs of epoxy took care of that. Works like a charm. Makes shaft alignment easy, none of this popsicle stick wedging, though that works just fine.

I ramble too much, sorry. Still I would look carefully at the naked shaft. You have a unique set up and must plan your next moves carefully. I agree that the oversize shaft, while it may have replaced a bent original, certainly is a good thing with the 50HP. Accurate centering in the log is getting critical because you are running out of clearance room. No contact allowed. Carry on!

[Dieselram94]

If it is salt build up, it should scrape off and reveal nice and shiny bronze underneath. If it keeps going, deeper and deeper, then it would seem to be worse than salt.

So I am trying to wrap my head all around this. Sounds like an inch and a quarter shaft, clearly not original. So somebody replaced the original shaft, of whatever material, with an SAE bronze shaft. Wow. Maybe it was just laying around, like my mystical sailboat shaft. OK...So, now the cutlass had to be modified to fit. Not too tough using a stock 30mm and a little working to get it to fit the 1.25". So far so good. Now what taper is on it? Your accessibility may be different, but going to all that trouble to install an SAE shaft, I would certainly want an SAE taper on it. I am getting off topic. Sorry.
Poke around and see how bad the corrosion is. I am running my 36 HP VP engine at no more than 1000rpm at the shaft (2000 at the engine). It ain't perfect, having checked it on the lathe bed. I can live with it. With more HP and RPMs it might be a very different story.

I am not familiar with the bolt on shaft log you describe, but there are numerous ways to fix these issues. If I had to replace the log, I would certainly figure out how to convert to a standard cutlass set up. You've got to hand it to the Swedes though, with the original cutlass-in-a-ball arrangement that self-centers. Stefan, Albinmotors, offers a few non-standard cutlasses, 1" for sure, in addition to the 25mm and 30mm. Not sure about 1.25". I mention this only because there are a pile of knee-bone connected to the shin-bone issues when you start fooling around with bigger engines/shafts/couplings/shaftseals/ cutli/props AND now shaft log.

Way back when, if you have read any of my earlier posts, before I ever worked on the engine, I did replace a couple shot mounts and figured out how to install another cutlass bearing to serve as midshaft (sort of) support up at the top of the shaft log. Seven feet on a 30mm shaft with support only at both ends seemed a bit excessive. Finding something that would fit inside the tube and still fit the shaft was tricky, but I came up with an all rubber cutlass bearing for Beneteau sailboats. It was just a little sloppy in the tube, but a couple dabs of epoxy took care of that. Works like a charm. Makes shaft alignment easy, none of this popsicle stick wedging, though that works just fine.

I ramble too much, sorry. Still I would look carefully at the naked shaft. You have a unique set up and must plan your next moves carefully. I agree that the oversize shaft, while it may have replaced a bent original, certainly is a good thing with the 50HP. Accurate centering in the log is getting critical because you are running out of clearance room. No contact allowed. Carry on!

I appreciate the detailed reply, I will certainly find your earlier posts and read up on your second cutless bearing. I’ll try to find a picture of the bolt on shaft log I mentioned, of course with using something like that, it would be difficult but crucial to get it perfectly inline with the original stern tube. I think probably best to bolt it in as well as bed it in epoxy to keep it water tight.

The tiny bit of scraping/cleaning I did on the stern tube and shaft seemed to reveal solid non pitted bronze. I will clean it up a bit more, hopefully tomorrow afternoon. It’s hard to imagine it’s corroded as the tube is not electrically bonded...??
I will also taste the white powder and see if it’s salty. I need to get the shaft removed soon for sure. Next to the propeller is some light pitting on the shaft, but everywhere else I can see seems good. I’ll know more after I clean off some more of the white powder.

As far as the cutless bearing, it looks as if someone machined out the original ball to allow a sae cutless to be installed right now it’s a new bearing.

What’s really got me nervous with this is I’ve never seen salt build up a residue like this. Maybe it does if left stagnant in a cavity like the stern tube over many seasons?

Again, I really appreciate everyone’s advice on this.

[WillieC]

Neither is my shaft log bonded, nor do I suspect many are. There is just not a good place to do that, maybe at the upper end but I do not recall much being exposed there behind the shaft seal/stuffing box. Like you say, it is isolated.
Your modified cutlass is the real deal. Somebody figured that out, very nice. The originals appear to consist of a very large ferrule, like you'd see in a compression plumbing fitting, possibly heat fitted to the bronze cutlass. The rubber sleeve, even though it has a casting ridge around it, is straight and receives its shape from the ferrule. The new cutli (plural, sorry) from Stefan are machined from non-metallic resin fiber super, duper material. No corrosion forever and ever amen!
Check out the shaft, smooth out the ridges, align it and get in the water!
I'll see if I can find my earlier posts.
Here it is:
viewtopic.php?f=28&t=9044&hilit=upper+c ... g&start=15

[Dieselram94]

Thanks for the link! I did read through all those posts. Interesting about the through hull fitting used as a bearing.

Here is a example of the bolt on shaft log I mentioned. It’s intended for a rudder installation, however I don’t see why it couldn’t be used to repair a bad stern tube provided it was epoxied in as well as bolted and perfectly lined up with the old stern tube.

I did get just a couple minutes to investigate further the corrosion.
I scraped with a screw driver a bigger area and I can’t see or feel any pitting, however I couldn’t fit a wire brush past the shaft into the stern tube. So I wasn’t able to shine it up much. I did wire brush a spot on the shaft that had white powdery on it and I was able to slowly erase the white substance, again no pitting evident.

I tried to include better pictures taken after tonight’s scraping. Not sure if any pink is there though. We’re supposed to get a nor’easter this weekend otherwise I’d have this shaft out. I might try to get it out anyways though.

[dkirsop]

A wild thought here. Perhaps you have an air cavity forming at this location and heat build up from the stuffing box is resulting salt build up.

Try loosening the front band clamps and burping the rubber hose to expel all air from this location when you launch and see if this resolves the problem.

[Dieselram94]

I suppose it’s possible, last run with it it was dripping from the packing as it’s supposed to though. But having just acquired this boat I don’t know a lot about it’s history.

Being up here in maine with short seasons at least limits how much time it’s exposed to corrosion.

[dkirsop]

I doubt that your stern tube or your shaft is corroding. If they were then the deposits would be greenish in colour and as previously mentioned there would be a pink blush to the bronze components. What you are observing now could be salt crystal accumulation over years of use. I'd just clean it up and monitor the situation being sure to "burp" the shaft seal each time you launch.

[WillieC]

Totally agree with dkirsop. There is another fellow with a 27 that has serious work to do on his stern tube. You'll be fine.

[Dieselram94]

Awesome! thank you guys,
I’m defiantly feeling better about it!

[Beta Don]

A wild thought here. Perhaps you have an air cavity forming at this location and heat build up from the stuffing box is resulting salt build up.

That's certainly something to think about. Any boat that is trailered or which spends winters on the hard and is relaunchd every spring needs a quick and easy way to 'burp' the packing to get all the air out of the stern tube, or things can get very warm very quickly. Many dripless shaft seals have a vent fitting on them with a tube that runs up well above the waterline just for that purpose

I agree with everyone else that the white powdery substance isn't anything you need to worry about. I've seen it occasionally on other boats used in salt water

Don

[Dieselram94]

Thank you Don, it’s very reassuring to hear you’ve seen this white powdery substance before. I can’t wait to get the shaft out

[ssrig]

Just wondering if you did end up tasting that white substance? If so was it salty at all?
I have found myself tasting the water in my bilges to see if it was fresh water, salt water, fuel, coolant etc. not too sure this is a good idea though.

I was under the impression that going to a bronze shaft one would need to go to a larger shaft to keep the same strength as stainless but then I'm no metallurgist.

[dkirsop]

I doubt the shaft is bronze - probably monel which is similar in colour to bronze but stronger and stiffer than stainless also more resistant to corrosion in salt water. Monel makes for a better prop shaft so long as you have $$$

[Dieselram94]

Just wondering if you did end up tasting that white substance? If so was it salty at all?
I have found myself tasting the water in my bilges to see if it was fresh water, salt water, fuel, coolant etc. not too sure this is a good idea though.

I was under the impression that going to a bronze shaft one would need to go to a larger shaft to keep the same strength as stainless but then I'm no metallurgist.

I did end up tasting it. It was slightly salty, not as salty as I thought it would be. But then again the sample size I was able to retrieve was very small.