Rust shaft coupling

[StephenGwyn]

Hi,

I had my prop shaft replaced 6 months ago. As part of the replacement, they installed a new coupling. As you can see from the picture, in 6 months it's become quite rusty.
Now admittedly the engine itself is getting on the rusty side, but it's 42 years old.

Is this amount of rust normal?
Should the coupling be covered in paint/grease/something?

Thanks,

SG

[ndutton]

The standard of bare minimum

As part of the replacement, they installed a new coupling.

Who are they?

Is this amount of rust normal?

Raw iron or steel in this environment, I'm surprised it's not worse.

Should the coupling be covered in paint/grease/something?

It should have been degreased in a solvent bath, primed and painted (oil base paint) prior to installation. Anything you can do in situ at this point to check the rust will prevent things from getting worse until the next haulout when it can be removed and properly addressed. I suggest at haulout because although it can be removed in the water, reinstallation of the shaft into the coupling will likely require a little John Henry action at the prop end of the shaft (hammering).

Please remember I tend to take things to extremes but once done, they're DONE.

[Mo]

Google "fluid film". It comes in a spray can and I use it on the docks sitting in salt water for 6 months at a time. When it comes time to remove the pins they come out easily. Considering there is a possibility of salt water contact there my suggestion is to have a can around. Give it a good shot and it will stay lubricated and protected for months on end. I keep a can on my boat and it works great for just about anything.

I can tell you it works better than anything I've ever tried on my vehicles, equipment, wiring in exposed areas etc....the best I've seen so far. Other option is "rust check" but it not as good.

[Rbyham]

Maybe it is just me but the picture shows more wetness than I expect I have going on at my coupler. Would that make a difference? Maybe the stuffing box needs a couple turns to tighten? Just asking...

[Dave Neptune]

SG, everything is wet in the pic. Did you just rinse off or is that how it looks after running? If it is you have a leak somewhere and if yer' in salt water just rust away until fixed.

The water from the packing should not climb up the shaft (gravity) and would not get slung around it would just drip at the packing or run "back".

Check the hose fittings when running at cruise or good and warmed up on the dock lines if you can.

Dave Neptune

[StephenGwyn]

Who are "they"?

Canoe Cove Marina did the work.

Why is it wet?

It's winter here in the Pacific North West. The relative humidity is something like 110% There is a lot of condensation. But the only thing I've had rust that fast was the first two sections of the exhaust, which were made of cast iron. I've replaced it with stainless steel. A lot of the rust you see on the engine itself is actually residue from from those old pieces.

SG

[Mo]

Google "fluid film". It comes in a spray can and I use it on the docks sitting in salt water for 6 months at a time. When it comes time to remove the pins they come out easily. Considering there is a possibility of salt water contact there my suggestion is to have a can around. Give it a good shot and it will stay lubricated and protected for months on end. I keep a can on my boat and it works great for just about anything.

I can tell you it works better than anything I've ever tried on my vehicles, equipment, wiring in exposed areas etc....the best I've seen so far. Other option is "rust check" but it not as good.

I've seen the above Fluid Film online for 26+ dollars a can. Don't buy it. Should be able to find it for 9-14 dollars a can.

[StephenGwyn]

Update: I showed the above picture to the guys at Canoe Cove who installed it in the first place. They said: We should have painted that coupling. We'll that for you now, no charge.But your engine room looks wetter than it should be.

[Al Schober]

SG,
I've never seen a shaft coupling like that. It looks like the shaft is held in by those two bolts. Hopefully there's a key to transmit the torque, plus something to keep the shaft from pulling out in reverse. With my coupling, the shaft just slides in with a key for torque. A set screw sinks into a drill hole in the shaft to take the reverse force.
As to the rust, apparently the material of your coupling doesn't have much chrome or nickel to retard corrosion. For the outer surface of the coupling, I recommend an epoxy primer coating such as Interlux 2000E. Once this is on, paint to match. For the bore, coat with a heavy grease such as is used for water pumps - smear some on the bore of the coupling and the OD of the shaft at assembly. The traditional material for this use is tallow, which I've never used but believe is an animal fat with a high melting temperature.

[67c&ccorv]

That's why I like electroless nickel plating for metal parts - 316 stainless even better - monel better still - for the money good bronze is hard to beat.