Stern tube too small...

[druid]

Oh, the Joys of working on an OLD boat...

I measured the stern tube on my Ontario 32 with calipers and it was 2.00 inches. At least the part that wasn't covered by the stuffingbox hose... Once I took the hose off, I found that somebody had ground it down to 1.8-1.9 inches. I ordered a 2" stuffingbox, but it's pretty loose. The next size down is 1.75 inches, and I think it's easier (and safer) to build up than cut down.

I don't want to cut it off and put in a 2" pipe since that would really cause a weak spot. If it was a non-critical area, I'd just wrap a few rounds of electrical (PVC) tape on the pipe and call it good.

(there are some other complications with installing a stuffingbox in there, but I won't bore you with them...)

Any suggestions?
druid

 

[centerline]

is a 1-7/8" not available from another manufacture?.. that would be the size you need.

 

[kito]

Is putting in the correct 2" shaft log out of the question? He has already weakened the tube by cutting it down. Wrapping it in electrical tape would scare me to death. I would rather build it up with epoxy resin and 1708 cloth.

 

[druid]

Yeah, I'm leaning towards fibreglass cloth and resin. Epoxy would be too slippery and there's no issue with "glue-ness" where epoxy would shine. My concern is making sure the pipe stays round. Putting in a whole new shaft log would be a major undertaking and I'd be scared I wouldn't get it lined up properly. There MAY be an el cheapo unit that's 1 7/8, but I'm going with the Buck Algonquin.

druid

 

[centerline]

epoxy too slippery???... is this thought driven because epoxy is so much harder than polyester?.
The epoxy would be easier to work with because you wouldnt be hurried... unless you're in a hurry

 

[Scott T-Bird]

I think I would lean toward installing a new shaft log. You've already invested in a nice new engine ... I'd look at it as insurance. Although, I'm not sure what led you to remove the stuffing box hose to discover the problem. I'm actually growing more concerned about my stern tube as this is discussed because I didn't make any changes to it when I replaced my engine. I left the bellows for PSS shaft seal attached to the stern tube as we didn't need to remove the shaft entirely.
I always sleep much better, once a problem is identified, by replacing with new parts. If the log is difficult or just too time consuming to handle on my own, I would feel no regrets hiring experienced help, and put my mind at ease. I can't take money with me to the grave so I generally have no problem parting with it. Anyway, those are my thoughts based on my experience and general outlook. Working with epoxy or fiberglass is all fine and dandy, but there is no way I would trust my handiwork around a hole in my boat that has parts that rotate at great velocity.

 

[druid]

I removed the stuffingbox because it was broken. There's nothing wrong with the shaft log except it's a bit too small diameter - no need to replace (Ontario did things well - I doubt even a pro could install a new one as well). I'm going with building it up with fibreglass. It's only 1/10 inch, after all.

druid

 

[Ted]

Try looking at the PSS dripless shaft seal. They make bellow sizes to fit your shaft log.
http://www.shaftseal.com/en/product_categories/300000001?page=1

 

[woodster]

that stern tube is made out of some really hi tech stuff ...not your normal epoxy or polyester...sand it with a very coarse abrasive in order to help the bond

 

[Jalepeno]

Druid,
Epoxy is a much better choice than polyester. Epoxy will bond chemically to the existing fiberglass tube while polyester will not. Build it up with a bit of saturated glass cloth.

 

[druid]

OK, here's some more details showing for instance why I'm not going with a dripless seal. First, I doubt it's "hi-tech stuff" - polyester was "hi-tech" back in 1976. But as you can see, originally the stuffingbox was "fixed" (not floating) and I had to grind away a bunch of material to even get the Buck Algonquin in. How they managed to get the old one in and properly aligned is a mystery: although it does look smaller.
As for epoxy vx polyester: yes, if the shaft log was epoxy I would probably use epoxy for this. But remember: I'm just building up material - I don't need strength per se, nor am I using it as "glue" (as in a stitch-n-glue boat, where epoxy is required)
I took a bunch more measurements (the curse of having accurate calipers!) and most of the shaft is closer to 1.9 than 1.8. I think a bit of material to build up the end will be all I need to get a good seal with the hose.
I'm going out today with my trusty wooden engine mockup (complete with 1" wooden "prop-shaft") to check alignment between the stern tube and the cutlass bearing.

druid

 

[centerline]

I believe there is more worry/concern than is warranted...
at less than an eighth of an inch of slack, I would put some better quality clamps on the tube and call it done... I cant see the need for such a close tolerance in a thick walled rubber hose on a plastic tube that needs clamps to secure it.
1-7/8" rigid exhaust tube is often joined with 2" rubber exhaust hose, and if the truth were known, probably exactly how it is, and would have been in your case if you had hired it done by a yard....

the thick walled hose allows for a higher tolerance than a thin walled hose would...

 

[druid]

I believe you're right, Centerline. Although most exhaust systems have a "50mm" tube, you can only get 2" (51mm) hose. And I measured ID of the hose on the Buck Algonquin stuffingbox and it was 2.0" in one direction and 1.9" in the other. Maybe I should just put my calipers away and install the bloody engine!

But thanks for all the suggestions and feedback.

druid

 

[druid]

After adding a thin layer of fibreglass, the tube was about 1.9" all round, so I went ahead and lined up the stuffingbox. We'll see if she's leakproof when she goes back in, but it looks pretty optimistic...