Ruined prop shaft and corrosion questions?-gctid806571

[Cool_Beans]

Woe to thee whom buys a used boat and starts looking a little to hard :silly:

While working on my list of things I found wrong during my inspections. . .and comparing and checking it against my survey list of deficiencies. . .

. . .I'm coming up with a third list of things we both missed inch:

And this first one is a bit of a stomach turner :sick:

As the picture shows, there is a chunk of my stbd. prop shaft missing! In all the time I've crawled in and around the bilge, I'd swear I would have noticed something like that. And the reflective tape is right there where surveyor put it on to check the rpms, I assume it would have been in sight. The shiny part of the shaft made me think the engine shifted forward and revealed that spot, but I see no evidence of engine movement and I even ran the engine in gear and goosed the throttles a bit. The shaft didn't move one way or the other. There is newer stuffing box hose on there now, I just assumed the shiny was from when it was changed out. . .any advice, ideas, things to check? Can something like that be fixed? I priced out a new shaft and ouch!



This next question relates to underwater corrosion. I dove on the boat to check things out and brush off the zincs, etc. The port prop had 2 spots (one per blade) on it that looked like a thin black ring with pink in the middle, about the size of a fingernail, that I could scratch off. Never seen anything like before, in person or on the net. The shaft is zinc'd and is isolated with a shaft saver. No picture though, sorry

Advice, recommendations, things to check for, etc. are all welcome B)

[Norton_Rider]

I would be very concerned about the shaft damage. It can lead to breakage. A friend with a 32 Bayliner had a propeller shaft break and back out a number of years ago. The boat almost sank before he was able to plug the opening.

[boatworkfl]

That is a very clear sign of electrolysis in front of the packing gland, I think that may have also happened to your prop and shaft outside of the hull.

Do you maintain shaft zincs? Also you need to inspect your bonding system.

I have bonded shaft brushes on my shafts just fwd of the packing nut.

I only use 8 ga green jacketed tinned marine wire for bonding.

It also looks like you may have an alignment issue with the shaft and or packing, when did you last re-pack your shaft packing, I only use Teflon/flax. or pure Teflon-which will last longer-also called steam pipe packing.

If you buy a new shaft buy Aquamet 22 or better.

[Cool_Beans]

Electrolysis? Interesting!

I've only had the boat a month, the Zincs that are on it were from before the survey. They look mostly intact underwater (with pits), I brushed them off with a scrubby sponge. The port side packing gland had a broken bonding wire, I fixed that on saturday with a new terminal. Both shafts are bolted to plastic "shaft savers" which should leave them isolated, right?

I currently have a "grouper" zinc (a couple weeks now) clipped on the port strut bonding wire and wrapped/bolted (sans insulation) the stbd. strut and out the transom door. Every couple days I've brushed off a white film so I assume it is working?

Yes, alignment is one my list of things to break loose and check at haul out. I was hoping to put it off and get a summer of fun out of the boat, but if I'm replacing a shaft I need to make sure I can align it inch: I'll redo the packing then as well.

Are there any tests I can do to verify everything working as it should?

thanks!

[smitty477]

Has the boat sat for long periods of time without use?

That looks exactly like crevice corrosion which takes place much faster with lack of oxygen.

Not likely electrolysis....

It does not go all the way around the circumference so likely it was on the lower side when the shaft sat for long periods of time when the packing was over that spot.

Does not look too bad yet even though the pic makes it look poor.

If you can not see any further cracks I would run it the way it is and keep an eye on it.

These same sized and metallurgical shafts are used on the 4588 Bayliner with more HO and weight and do not fail as a rule so there is some safety factor there.

Bigger questions include - who and why did the packing shift. Is the shaft aligned? Are the engine mounts secure? - hard to tell by just looking as the rubber and bolts can shift when under load. How are the struts , cutlass and strut bolts?

"The shaft is zinc'd and is isolated with a shaft saver"

Is that why the shaft packing is shifted back? Why were they installed recently?.

Without other pictures and information it is hard to tell what overall is happening back there.

[boatworkfl]

The crevice corrosion on the shaft is what I consider deep. keep a close eye on it, I would replace it, a broken shaft often means a new prop.

[Alan_Teed]

My 2 cents: I think both Smitty and Pat offer good advice (although conflicting). If you want to run through the summer and are prepared to run at lower RPMs and can live with the worry of a potential serious issue - deal with it later. But fabricate something that can plug the hole if it were to fail and accept that this is a possibility. If the above will leave you worrying constantly while you are running the boat (it would me) then fix it now and enjoy the summer - you will have to replace at some point anyway so it is not a matter of avoiding the expense ~ just the timing of it,

[smitty477]

I agree to be careful for sure. I blew the picture up as large as I can and cannot tell how deep it is - these are 1-1/2" Aquamet so nothing like the 1-1/4" bronze shafts I have seen on some similar hp boats in the past.

Those 1-1/2' shafts are the exact same (only shorter) as the 4588's with larger props , higher gear ratios , heavier boat and more hp and torque.

I have seen some really deeply grooved shafts (360 degrees) that had their grooves 'hidden' by the packing lands for years do OK.

Not a reason to fall asleep or not be concerned but I see more serious damage caused by many other things like : failed engine mounts, rubber cutlass separation , shaft alignment, strut anchoring, bent shafts, poor prop installation , bad prop shaft broach or key, and poorly balanced props.

FWIW -If memory serves me well I believe that if the shaft broke at that location the prop would only move back about 6-8 inches before contacting the rudder - these are 4 blade props at that point the shaft will not have left the shaft tunnel.

Anyway - whatever you can do to figure out what it really is and how it got there would be helpful.

Crevice corrosion will be surface down while electrolysis will be more of a perforation and hollowing out.

heading out of town so good luck with the problem search....

[Norton_Rider]

I would definitely not run that shaft as is, slow speed or not. If you really want to run it I would do a dye penetrant inspection of the affected area. If the inspection reveals no cracks, the area should be carefully dressed to eliminate any stress risers.

[Pcpete]

Beans, see if there's a friend of a friend who can come down and do a dye penetrant and eddy current test on that shaft in place. They are nondestructive tests for cracks similar to magnaflux but for non ferrous metals. I agree that looks ugly and you may be able to find a good used shaft at a more reasonable price.

As to the alignment, if you are talking about the alignment of the strut cutlass bearing to the transmission shaft using a laser, that part is an out of the water operation. If you are thinking shaft to transmission coupler, that's an in the water after at least four days of being in the water after ther hard. The boat can change significantly when it is supported on stands, then changes back slowly after relaunch. You could check the coupler alignment tomorrow assuming you haven't been lifted out in the past week or put it on a mudflat to paint the bottom.

I have shaft brushes that are nothing more than an electric motor brush soldered to a chunk of copper strap that is mounted to a stringer and presses on the shaft with a green bonding system wire connected as part of the engine brush mount. The brush rides on the shaft with about five pounds of force so the prop, shaft and nuts are all bonded to the rest of the underwater gear.

Keep after it, I'm working through my abridged list number three.

[boatworkfl]

Very good advice on the shaft alignment statement, I always recommend checking shaft alignment at the coupler after the boat settles back in the water, that hull does move some.

The shaft brush will make sure the under water metal is all bonded together. Is all the under water metal zinced and bonded, including your swim step supports?

What length shafts do you have? I am guessing 60"

[Cool_Beans]

How long is "sitting for long periods of time"? Looking over some older log books, maybe every other weekend when it was warm, then the last owner used it mostly as a crash pad and gin palace for the last 4-5 years. He did start the engines every couple weeks and dropped them in and out of gear. . .so he said.

Stbd. strut was pulled last year and cutless replaced. The shaft savers are god knows how old. . .the hurth450 trans were replaced with ZF63a's some 10 years ago though, might have something to do with them?

What other pictures might be helpful? And are there any tests I can perform in the water? Possible electrolysis has me a little spooked.

I really didn't want to mess with it this year but I might have to bite the bullet and just drop the boat in a yard for a couple weeks while I align everything and have all the running gear checked out inch: Slow trawler runs might be fine for local summer fun, but I want to do some serious fishing this fall and yes. . .I would be worrying about breakage on a 2 hour run out to the tower.

Are good used shafts possible to find, and enough of a costs savings to persue that route?

Thanks all

[boatworkfl]

"Cool Beans" post=806869 wrote:
How long is "sitting for long periods of time"? Looking over some older log books, maybe every other weekend when it was warm, then the last owner used it mostly as a crash pad and gin palace for the last 4-5 years. He did start the engines every couple weeks and dropped them in and out of gear. . .so he said.

Stbd. strut was pulled last year and cutless replaced. The shaft savers are god knows how old. . .the hurth450 trans were replaced with ZF63a's some 10 years ago though, might have something to do with them?

What other pictures might be helpful? And are there any tests I can perform in the water? Possible electrolysis has me a little spooked.

I really didn't want to mess with it this year but I might have to bite the bullet and just drop the boat in a yard for a couple weeks while I align everything and have all the running gear checked out inch: Slow trawler runs might be fine for local summer fun, but I want to do some serious fishing this fall and yes. . .I would be worrying about breakage on a 2 hour run out to the tower.

Are good used shafts possible to find, and enough of a costs savings to persue that route?

Thanks all

I would buy new and be sure of what you are buying!

How long are your shafts? boatworkfl

[NeilW]

I agree with Smitty that it is definitely crevice corrosion aka anaerobic corrosion as the bronze stuffing box is a normal green color rather than pink, and it would have gone much faster. I also think you can run all you want with the present shaft and it will not break. But the corrosion will slow down if you lubricate the shaft more often by putting it in gear even when at the dock letting O2 get in contact.

I see broken shafts all the time, and never from that little of corrosion. This is what I do for a living.

[boatworkfl]

"NeilW" post=806878 wrote:
I agree with Smitty that it is definitely crevice corrosion aka anaerobic corrosion as the bronze stuffing box is a normal green color rather than pink, and it would have gone much faster. I also think you can run all you want with the present shaft and it will not break. But the corrosion will slow down if you lubricate the shaft more often by putting it in gear even when at the dock letting O2 get in contact.

I see broken shafts all the time, and never from that little of corrosion. This is what I do for a living.

I agree, but I would buy a spare shaft, that being said, I cannot understand why any inboard boat would not have a spare shaft.

I have a friend in Seward AK that lost his charter boat due to an electrical fire while I dry dock, a year before he hit a dead head and lost the prop and tail shaft. he was wondering how long it wouls take to get a shaft sent up from Seattle, I said 3 days, that being said I asked did you check the spare shaft storage pipe, he said what?

I told him that boat had a fiberglass pipe in the port lower corner of his transom, we unscrewed the plug and there it was, a brand new shaft.

The next day he had a full 6 pack halibut charter-he made it.

Always have a spare shaft, just as many of us have spare props.

You can save the corroded shaft for an emergency, I have a spare shaft, as well as a much longer shaft I can cut down to 60"..