Stern tube A25

[Dieselram94]

Just wondering after reading a thread about a different brand boat... has anyone seen a A25 with a corroded/worn through stern tube? The thread I was reading was about the corrosion of the stern tube up by the stuffing box enough that it was leaking water and then broke off. Just wondering if I should add a zinc or a ground wire to the stern tube? I don’t believe mine has any issues, but I haven’t taken the stuffing box off to inspect. That will come soon enough as I’m going to have a new shaft made. Currently I have a 1.25” shaft running through I think stock cutless bearing holder with a 1.25” cutless bearing. My shaft seems to be worn slightly undersize where it rides on the cutless bearing. It measures about 1.22” so some slop in the shaft. Shaft seems to be bronze and some corrosion showing by prop, although doesn’t seem extensive.

[DesertAlbin736]

Here's a look at our stern tube with stuffing box (old fashioned with flax packing) loosened & moved forward. At the time I was checking the shaft alignment with the AquaDrive thust bearing & making sure the shaft was centered within the stern tube. Didn't notice any noticeable signs of corrosion. #No corrosion!

20171115_113303_resized.jpg

[Dieselram94]

Thank you for that picture. I think I will slide my stuffing box ahead and check it. I have just the flax packing as well. I know I’m going to replace the shaft, I’m strongly considering a aqua drive as well. My motor mounts seem soft and allow the motor to wiggle a bit. Can’t be good. Probably part of the reason the shaft wobbles. But at the price I paid for the boat, I knew I was probably reshafting. I’m thinking maybe I should go with a one inch shaft instead of the 1.25” it currently has for more stearn tube clearance and just order the cutless from Albin motor.

[Dieselram94]

Finally got a few minutes to slide the stuffing box forward. As far as corrosion all looks well!!! Thank god!! However shaft alignment is way off! Shaft is almost touching inside edge of stern tube on one side but lots of room on the other side. Looks as if I need to slide motor to the side.

[Beta Don]

If after 40+ years, your shaft is only worn 3 thousandths where the rubber cutless bearing touches it, I would just change the cutless bearing and motor on! No need for a new shaft because of the missing 3 thousandths. There are probably a dozen better places you could spend that money!

Don

[Beta Don]

A quick and dirty primer on how to do an engine/shaft alignment . . . . for anyone who has never done one

Remove the bolts which hold the shaft coupling to the transmission flange and slide the shaft aft 1/8th inch or so. Slide the packing forward like you have it now and use small slivers of wood to center the shaft in the stern tube - Now the shaft coupling is the reference for all motor mount adjustments. Do not do anything to 'un-center' the shaft after this

Adjust the engine/trans as necessary to make the transmission flange parallel to the shaft coupling. Use a popsicle stick or something to check the space between the mating surfaces at 12 o'clock, 3, 6 and 9, adjusting your motor mounts to get it closer and closer, so the stick touches equally at all 4 points

When you get it close to 'right' CAREFULLY slide the shaft forward (without disturbing your centering shims) until the coupling touches the transmission flange and continue adjusting, using a feeler gauge between the coupling and the flange. When you get it to where a small feeler gauge (.005 or .0075) has equal drag all around the gap between the coupling and the flange, your engine/trans is adjusted perfectly inline with your prop shaft. Tighten everything down and button it all up

Many marinas either do not have a mechanic capable of doing this correctly or they just don't care to spend the time to do it right - This is one area where a carefully done DIY is frequently better than paying a 'pro' several hundred dollars to do a half assed job - I have seen TERRIBLE alignments done by otherwise great marinas

Don

[Dieselram94]

A quick and dirty primer on how to do an engine/shaft alignment . . . . for anyone who has never done one

Remove the bolts which hold the shaft coupling to the transmission flange and slide the shaft aft 1/8th inch or so. Slide the packing forward like you have it now and use small slivers of wood to center the shaft in the stern tube - Now the shaft coupling is the reference for all motor mount adjustments. Do not do anything to 'un-center' the shaft after this

Adjust the engine/trans as necessary to make the transmission flange parallel to the shaft coupling. Use a popsicle stick or something to check the space between the mating surfaces at 12 o'clock, 3, 6 and 9, adjusting your motor mounts to get it closer and closer, so the stick touches equally at all 4 points

When you get it close to 'right' CAREFULLY slide the shaft forward (without disturbing your centering shims) until the coupling touches the transmission flange and continue adjusting, using a feeler gauge between the coupling and the flange. When you get it to where a small feeler gauge (.005 or .0075) has equal drag all around the gap between the coupling and the flange, your engine/trans is adjusted perfectly inline with your prop shaft. Tighten everything down and button it all up

Many marinas either do not have a mechanic capable of doing this correctly or they just don't care to spend the time to do it right - This is one area where a carefully done DIY is frequently better than paying a 'pro' several hundred dollars to do a half assed job - I have seen TERRIBLE alignments done by otherwise great marinas

Don

Thank you for the information! My engine mounts have no provision for moving the engine side to side, so I was thinking I would ream the hole where the stud from the mount passes through the engine bracket a bit so I can get the motor centered in the boat better. I can’t movd the mounts themselves as they are basically against the sides of the engine pan. This motor barely fits inside the doghouse. Definitely a larger choice for this boat! Lol
My shaft also has a bit of runout (haven’t measured it yet) but the stuffing box wobbles a substantial amount. How much runout is allowable?

[WillieC]

How are you determining your runout? Mine had a good quarter inch and it was all misalignment/soft oil-soaked and broken mounts. As to side to side adjustment...the old VP mounts didn't allow much. Oversizing holes in any or all of the mounting bolts involved should get it.

Once I got around to ordering a new prop, I took the shaft to the prop pro and he dialed it up on his lathe bed. Mine was indeed bent, the prop end clearly indicated a strike of some magnitude. There was some ten thou in the middle which was easily corrected, but the damage at the end would take a new shaft. I'll get a round tuit as soon as DA loans me his and the cash for a new shaft!

[tribologist]

1.250-1.227 is 0.023. That seems like a lot of wear of wear. Did you check the diameter in an unworn area so that you are confident of the reading? I never trust digital calipers that don't say Mitutoyo on them.

The spec for runout for a 10 ft shaft supported 2" from the ends is 0.017" That is certainly visible but I don't know if it would be close to "substaintial amount" . Lots of good info here.. http://www.pacificmarine.net/engineerin ... -shaft.htm

It looks like you have decent distance from the cutlass bearing to the prop. You could possibly consider shortening the shaft to get the un-worn area into the bearing. A new shaft is probably running $700-900 so it is worth putting some effort into fixing the one you have.

I would think the shafts for the A25 is simply 303 stainless. That is very ductile and should be easy to straighten. (

By the way, the prop nuts are on backwards. The thin one goes next to the prop. The outer nut takes all the load so you want the bigger one there.

Ulf

[Dieselram94]

I used my metric dial indicator today on the shaft where the stuffing box goes. I measured consistently .7 mm of runout when turning shaft by hand taking care not to pull on it whatsoever.

I have measured a unworn area of the shaft and it hit exactly on 1.25” so I assume my caliper is accurate. I have a brand new cutless bearing installed and I can feel a very slight amount of play between shaft and bearing when wiggling the prop. Doesn’t seem overly excessive to me though.

I still have yet to get enough time to try to align the shaft properly though. It is definitely not centered to the stern tube at all, as it’s almost rubbing one side of the stern tube...maybe a few thousands clearance on that side and a good 1/4-3/8” clearance on the other side between shaft and stern tube. I think I could live with the shaft if I could get it running slightly more true.

On a side note, there is a fair amount of white powdery residue inside stern tube and some on the shaft, which is also bronze by the way. I cleaned a tiny spot inside stern tube with a screw driver and didn’t see any pitting. What is this residue? Just salt build up or signs of galvanic corrosion?

[WillieC]

Looks like pink on bronze shaft, hard to tell from photo. Does not that indicate de-zincification, and perhaps the source of white powder?
Not too many bronze shaft owners still out there, or at least reporting in.

[Dieselram94]

I’m in a tough spot as I’m color blind
The powder is on the shaft and inside stern tube
I’m hoping it’s not anything serious

[WillieC]

I had pink on my old prop which, according to the folks with an $800 prop to sell, was the death knell. Prop was made in mid eighties so it served well, sitting in marinas all those years. The new prop I bought has no pink on it, but weighs about half as much, slight exaggeration, which suggests to me the original prop had plenty of pink to give! What I didn't want was a blade falling off mid excursion.

These old 25s are somewhat overbuilt, pre CAD days. Were I you, I would remove that bronze shaft and drag it out for second or third opinions. But we already know what the consensus will be. Hopefully that acknowledgement is of professional assessment and not cynicism. The shaft is easy to replace, around $800, new unobtanium alloy, I forget what they call it. Better than SS, carbon fiber, depleted uranium, and red kryptonite combined. Alternately, depending on how lucky, clever, and patient you are, you might find a decent used shaft out of a sailboat, long enough for you to modify to your satisfaction. (Are not the bronze shafts more prone to deformation, being bronze and all? Maybe fine for the AD21s, maybe not for the 36HP VPs? Another point, possibly, for upgrade.)

In my perfect world, I would like a brand new shaft, manufactured, balanced and straightened in a zero gravity environment, with an SAE taper that would fit off the shelf replacement props from any West Maroon or Fred Meyer fitted to my brand new Beta/Yanmar/Sole/VP/Mitsubish/Cummins/DD normally aspirated non-turbo tier three (or four or five) diesel engine driving the generator for the electric servo motor with state of the art maintenance free battery bank. Installation by others with eternal warrantee.

All that and still fit the oddball cutlass bearing. Hell, have them rebuild that for a standard 'Merkan bearing while you're at it.

Now the bronze shaft tube...
With the shaft out, you MIGHT be able to assess any damage to it. And what would that mean? Water intrusion into pretty substantial fiberglass layup? They make fiberglass shaft logs nowadays. Worst worst absolutely nightmare worst case, the log can be drilled out and replaced. (I don't enjoy fiberglass work, but it is doable.)
It would have to be pretty bad with lots of internal damage from leakage for me to get too excited about replacing the tube, as long as the upper end still accepts the stuffing box/shaft seal device.

Do not lose heart. Yet.

She's a good old boat and she'll stay afloat
Through the toughest gale and keep smilin'.....Gordon Lightfoot

[Dieselram94]

WillieC, thank you for the reply any chance you think the white powder is salt residue build up? I think I should taste a bit and see if it’s salty? I cleaned a spot on the shaft and found no pitting, same thing in a tiny little spot on inside of the tube. The stern tube does feel very solid though.
Im definitely in love with this boat. Even if the tube was to be bad (although I think it’s probably ok) I would fix it. One thought I had was one of those shaft logs that bolt into the inside of the hull with two bolts and then a stuffing box could be mounted. Any idea what a full tube replacement would cost at a yard?

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

[DesertAlbin736]

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.