Prop shaft coupling

[finefurn]

Seems my prop shaft coupling has developed some serious rust. This was a supposedly a new coupling 6 yrs ago when the cutlass bearing was replace.
I bought the boat 3 years ago and at that time this coupling still had a full coat of bright paint on it. It's not readily visible so I never paid any attention to it. chasing a diesel leak let to this discovery. The coupling is badly rusted with heavy scale. Tapping on it it still seems solid but this heavy scale has me concerned. How long do these thing last before you would consider replacement. Could I get another season out of it and replace in the fall. How big a job is it to replace it. Typically I only run the engine about 50 hrs a year. The boat is a Hunter 27 powered by a Westerbeke 12b2

[sailorboy1]

Brush it clean and paint it

[mike d.]

I would say your stuffing box is letting in to much water ! IE spraying gently ? This is only based on the pic ! I would take it off and clean it, then use a heavy zinc based primer, then a good quality paint !

[sailorboy1]

Well I definitely would not take it off unless you are going to replace. If there is any corrision inside the coupling and you put it off the scale will come off and it will be loose on the shaft after.

[Bellinghamster]

Probably still solid under the scale. As other said, clean it up as best you can and get some paint on it (apply rust converter like Ospho before painting). Unfortunately, the short clearance between coupling and shaft packing nut will probably mean changing it will involve sliding your engine forward or lifting the back of your engine/transmission high enough to get a puller on the coupling to get it off the shaft. I've removed couplings with a bit more clearance by seperating it from the transmission flange, inserting incrementally longer spacers centered on the shaft and using longer coupling bolts to draw the flanges together, thereby pushing the shaft out the back. This does carry the risk of deforming the transmission output flange, losing the shaft out of the boat, and a lot of difficulty getting the new coupling onto the shaft since there is very little shaft to "hang on to". i.e Best done out of the water. Then you can have the new coupling properly fitted/faced on the shaft. Prepare a few weeks in advance by periodically squirting penetrating oil (Kroil or similar) on the coupling bolts and coupling-to-shaft to help it move easier.

[Manateeman]

You have four clamps on that short piece of hose. If they break a lot of water will come in the boat. 316 stainless ABAW rolled edge solid not slotted band or tee bolt.
Please do this first. I’d also consider replacing the shift cable and the special clamps and paint the support bar. While you are under there, change the transmission fluid.
That transmission is 1 or 2 k$. If you are going to change out the coupling I’d look into a two bolt split one...change to a Last Drop stuffing and bring the shaft and all the bits to a machine shop. Please take a look at the Marine how to pages or search here for threads on fitting the prop to the shaft.
If the shift breaks in gear as you are docking, it’s not fun.
Two of these items, the band clamps and the tranny fluid, should be done soon.
If you don’t have a lot of movement / vibration, and the coupling is solid on the shaft, clean and paint and you’ll be ok for a while. Check the stuffing box isn’t getting hot or leaking a lot of water. A Last Drop keeps the salt water spray from rusting everything. You might ask Santa for a drive saver too.
Happy trails to you
Mark and the manatee crew.

[Knotical]

Mine was rusted too albeit not as bad as yours, with your very little engine use I say it would be ok to go through the season, I would brush clean it, paint it and monitor it. Like you, I had very little space between the coupling and the stuffing box but I was due to replace everything including shaft and cutlass so just waited until haul out.

[Stu Jackson]

It's a heavy chunk of metal. It ain't goin' anywhere. Find out where the rust is coming from: most likely an inadequately adjusted stuffing box spraying salt water around. Adjust the box, clean the coupling. Good luck.

[wingless]

That steel coupling may be polished up to look like chrome.

That part is fine, just surface rust.

When I do those parts I first polish to a chrome finish, then apply Pettit 6455/044 Metal Primer, followed by epoxy barrier coat, then Rustoleum Professional Aerosol Spray Paint,

The result is a looong lasting glossy plastic finish, even in this marine environment.

It is common for the hose clamps to each have opposite orientation, rotated 180° position.

It is useful to lap the coupling to shaft using lapping compound when disassembled.

[Jim Cate]

Just a thought: The hose from stern tube to stuffing box looks longer than necessary to me. Might well be possible to shorten it a few inches, moving the place where water leakage comes from the stuffing box further away from the coupler. That plus a careful adjustment of the box could improve longevity of things a bit, and for essentially no cost.

You could also repack it with one of the teflon based packings. These allow you to tighten the gland up further, to the point where it does not leak at all, without harming the shaft. Good stuff, and not expensive.

Jim

[Reefmagnet]

I wouldn't be inclined to paint because paint won't adhere to rust scale all that great. If you coat it with something like Tectyl, it can be easily recoated as needed.


https://tectylproducts.com/

[Manateeman]

Teflon packing is an excellent suggestion. Dig out all the old stuff...water might come in but you can manage that...polish the shaft a little bit ..if..it feels rough or dirty..the section where the packing touches. A dental pick , tweezers to get the old stuff out. Clean the inside of the nut. Stagger the packing but don’t squeeze it too tight. Run it in gear both directions. Don’t overtighten.
Please get some new non slotted clamps and tend to the shift cable.
We have changed from traditional packing to Last Drop in the water...not for the faint of heart and we scuba so we rigged it so the prop and shaft would not fall out of the boat. LOL. Seen that happen!
Teflon packing comes in different thickness. Get the right one...it’s great stuff and will stop the salt water shower on your transmission and engine.
Manatees say hats off to our learned moderator.
Mark

[wingless]

Originally Posted by Reefmagnet

I wouldn't be inclined to paint because paint won't adhere to rust scale all that great. If you coat it with something like Tectyl, it can be easily recoated as needed.


https://tectylproducts.com/

They have lots of products.

This one says clean and rust free first.

Which product protects a rusty part?

[Reefmagnet]

Originally Posted by wingless

They have lots of products.

This one says clean and rust free first.

Which product protects a rusty part?

506, I think

[finefurn]

Thanks all for all the great reply's. I now got a plan on what to do. Years ago I restored several old cars, as a rust preventive on frames and underbody I used POR-15. that seemed to work well. Don't know how it would work in the Marine environment. Anyone ever tried it?