Pitted Prop Shaft Repair ?

[sww914]

All good points here. Torque, yes. If my customer's racecar has say 250 ft lbs of torque at the rear wheels and my diesel has 100 ft lbs of torque at the flywheel through a 2:1 transmission it's looking pretty equal isn't it? No way I would send one of my guys out on the track with and axle that's missing that much strength.
Any guesses on price or supplier recommendations for a 1 1/2" X 8 1/2' shaft?
Or are you guys going to make me do my own legwork?
So far my fear of price is based on the opinion of 2 guys hanging around the boatyard flapping their lips.

[sww914]

BTW, I already have a dripless shaft seal that I'll be re-using. It appears to be in perfect shape.

[DeepFrz]

Gosh, the tool of choice is called a "Search Engine"...

Let us know what you find out.

[Cotemar]

sww914,

I would recommend replacing your propeller shaft.

If your propeller shaft breaks you may have a 1-1/2” hole filling your boat with water as the shaft slides out of the shaft tube.
Your zinc’s may stop the shaft from hitting and jamming your rudder if you’re lucky.
Proper maintenance lets you sleep at night.

Mark

[fstbttms]

Originally Posted by sww914

So far my fear of price is based on the opinion of 2 guys hanging around the boatyard flapping their lips.

If I had a nickle for every piece of absolute @#$#%^# I've heard on the docks...

[redmirage]

Bead blast it and take a closer look. I had pits in my shaft that looked bad until I blasted it. They were quite minor. I was able to place a coat of west epoxy and glass over the area and it still looked great five years later.

[sww914]

I got 2 quotes so far.
$550.00 from the first place
$579.00 - $799.00 depending on which alloy I chose.
That's for a 8 1/2' X 1 1/2" shaft with a taper.
Not too bad, certainly not the $1200.00 - $1500.00 that the bonehead boatyard spectators quoted.
I think I'll buy a new shaft.
The pits are certainly deep enough to compromise the strength.

[Maine Sail]

Originally Posted by David M

The reason this has occurred is the lack of oxygen to the stainless steel. I know it sounds counter-intuitive, but stainless steel needs oxygen to help prevent it from going active.

One solution would be to get a drippless shaft seal with a nipple that allows pressurized sea water from the engines cooling system to be injected into the area between the cutlass bearing and the shaft seal.

I realize this is the last thing you want to hear because of the cost but it is something you could add in the future when replacing your corroded propeller shaft.

My buddy owns a shafting shop and has noticed a HUGE increase in shaft log area corrosion of both pitting and crevice corrosion. It is due to the water trapped up in there becoming oxygen deprived. Allowing the seal to drip, with traditional packing glands, allows the water to stay better oxygenated. A PSS with the vent line will keep the water in the log at the same oxygen content as the rest of the ocean, or darn close and thus drastically minimize this issue. A direct plumbed PSS will add oxygen with the motor running but depending upon the plumbing may seal it off with the motor shut down. With the advent of Gore type packings, miracle clays, Syntef lubes and folks thinking "drips less" means dripless there will continue to be a growing problem with stainless, aqualoy & nitronic shafting suffering crevice corrosion. Shafts need air and a vented PSS or a dripping stuffing box can provide this. Cut of the flow and the supply of oxygen and you run a risk of destroing your shaft.

I would not trust that shaft. Saving it, to save money, may be an expensive mistake. $550.00 is a good deal but I would go for Aqualoy 22 especially given your vessels propensity to starve the water of oxygen.

[David M]

I hope you understood what I meant by drippless... The PSS type of seal with the water injection

[Maine Sail]

Originally Posted by David M

I hope you understood what I meant by drippless... The PSS type of seal with the water injection

If you were referring to me then yes I understood. Either type of shaft seal, traditional packing or PSS style, should either vent air or drip enough so as the water does not become stagnant in the shaft log. A "plumbed" version of a PSS may not prevent oxygen starvation with the motor off depending upon how it is plumbed but one vented to the atmosphere well above the waterline does a good job.

Another problem I have seen numerous times with people who make their stuffing boxes completely dripless is that air can get trapped up in the shaft log from quick blasts of reverse and the resulting cavitation bubbles. With no way to displace the air because it is sealed up tighter than Fort Knox eventually the packing runs completely dry and cooks it. Same used to happen on certain boats before PSS made all their seals vented or plumbed. A vented shaft seal or slightly dripping stuffing box can be a good thing for a number of reasons.

[cal40john]

I'd always been told that a properly adjusted stuffing box dripped a little while motoring and didn't when stopped. The boats I've sailed on have been adjusted to this standard. Sounds a lot like the PSS seal as far as exchange of oxygenated water.

John

[Laidback]

One successful repair I have seen is sleeving the area of corrosion with a substantially thick walled sleeve. This was done on a friend's Catamaran that had 2 extraordinarily long prop shafts.
In this case one would need space between the coupling and the cutlass in which to insert the sleeve and weld it to the shaft.