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post #1 of 11 Old 12-27-2014 Thread Starter
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Stern tube grease and propeller shaft

Hi everyone,

After having visited this forum many times since I bought my boat three years ago, I now feel myself obliged to post a first thread, hoping I will find great advises as it is so frequent here. I ask you to be indulgent for my English, because it is not my mother language.

So, here's my situation:

Last autumn, to give me the opportunity to make some maintenance work on the engine and the engine room, I pull out the engine from the boat and remove the entire propeller shaft, stuffing box and cutlass bearing system. I will change the stuffing box and the hose attached to the stern tube and also the cutlass bearing. I'm planning to put a Duramax Cutless bearing (the same that was previously there) and I don't know exactly which stuffing box I'm gonna choose.

As I was removing the propeller shaft, I was surprised to find that the entire stern tube was filled with grease. The owner from which I bought the boat, and all my friends at the boatyard never told me anything about the fact that there was grease in there and - so I'm concluding - it has to be refill periodically. Since three years I have the boat, I have never done that maintenance part (by ignorance), but everything seemed to work fine until now, and the propeller shaft shows no sign of wear.

However, as I am now aware of that fact, I start searching on the Internet for what kind of grease and what amount I will need to put back there when I'll be reinstalling the whole thing next spring. As I get more information, more confused I begin to be (as it is so often the case with sailboat). I've read that putting grease inside of stern tube was not recommended, because it will prevent sufficient water flow to reach the stuffing box and cooling it. I've read the comments of many people that seem to have the same type of installation as me and that were saying that a grease-free installation works fine. Others say that, because there was already grease there, it needs to have some, and that "a small amount" (without any further precision) would be sufficient.

I know that my boat is quite old, and that previous owners had done very amateurish work on it. I know that the engine has been replaced in 2002 by a Yanmar 2GM20, but I don't know if the propelling system has been replaced at the same time. I am wondering if the grease could have been put there in a previous setup, and been kept in place after having change some parts, not making it necessary anymore. I'm also wondering, in the case that greasing is necessary, if I need to clean all the old grease from the shaft and the tube before putting the new one, or if I could leave the old one in place.

What do you think about that and what will you recommend me to do?

Thanks in advance!
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post #2 of 11 Old 01-17-2015
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Re: Stern tube grease and propeller shaft

Hi, none of my boats have had grease in the propeller shaft tube. It is correct that water must get to and weep through the packing gland to keep it cool, unless it is one of those new dripless types. I really don't know what the grease would be lubricating and if it was mine I would remove the grease.
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post #3 of 11 Old 01-17-2015 Thread Starter
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Re: Stern tube grease and propeller shaft

Thanks Cal31 for your answer. The only thing about which I would like you to give me more information is when you say :

Quote:
Originally Posted by Cal31Windchaser View Post
I really don't know what the grease would be lubricating.
In my mind, I could understand that grease might be needed to prevent the shaft from "rubbing" to hard against the tube. Except for the cutlass bearing at the end, I don't have any other bearing in the tube. So, I'm assuming that the rotation may cause some wear on the shaft and/or the tube. Yes, the shaft is not so tight in the tube, and I'm assuming that I should try to center it as much as possible when I'm gonna put it back in place, but with the engine vibration I could hardly imagine that the shaft will never touch the tube under charge.

So if you could just give me your light about this, it will probably help me to clarify the situation and ease my mind.

Thank you,
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post #4 of 11 Old 01-17-2015 Thread Starter
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Re: Stern tube grease and propeller shaft

This post is meant to reply to a PM that CalebD sent to me. Unfortunately, the system doesn't let me send PMs because I don't have a sufficient number of post published. Sorry for the bypass :

" Thanks CalebD for your help.

This is exactly the kind of box that I already have. The only thing is that there is a little pin at its end, just before the flexible hose, where, originally, I'm assuming it was needed to add grease. Now, this pin is just a whole bunch of rust.

I was planning to change the stuffing box with one of the same type (so thanks for the link, it gonna be really useful). It is also perfectly clear for me that the original setup doesn't respect the actual environnemental regulations.

However, what I am wondering about right now is that: if the way the tube and the shaft were originally designed required to have grease, should I just put the grease thing apart without causing wear to my boat ?

I would be pleased if you could help me to clarify that issue.

Thanks,

Julien"
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Re: Stern tube grease and propeller shaft

Julien, not sure what CalebD sent you but it sounds like he might know more about your particular boat model and situation. I was just saying that if my prop shaft had so much lateral movement that it was intermittently contacting the stern tube I would be extreemly concerned. If the tube and shaft are not designed to rub against each other, no amount of grease will protect it. I have never seen that amount of lateral deflection on my prop shafts. On my boats the stern tube simply provided a hole for the shaft to go from inside to outside the hull, and have required clear passage of water up the stern tube to lubricate the packing.

If the mystery can't be fully resolved by someone else on the net, I would highly encourage you to have a knowledgeable boat mechanic look at it.
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post #6 of 11 Old 01-17-2015
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Re: Stern tube grease and propeller shaft

The shaft should not rub in the tube.

As far as grease it is very common in the UK. I have owned 2 UK built boats with stuffing box greasers. Usually a remote greaser is installed and before starting a quarter turn is made. Stays cool and doesn't drip.
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post #7 of 11 Old 01-17-2015
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Re: Stern tube grease and propeller shaft

Paging Mr. MaineSail.

I'm not sure why I PM'd you instead of posting in the thread.

Mitiempo (Brian) confirms that the greased shaft set up is either regional (British) or as I indicated before, old school.

The water pump on my engine (Atomic 4) had a grease cap fitting that lubricated the shaft of the pump. I got a new pump that does not require grease for the pump to work properly. I am not a fan of extra systems that require periodic greasing/maintenance. These are precisely the kind of things that get overlooked. I feel the same way about your greased shaft set up. Why bother when most boats simply use water for lubrication and cooling of the shaft and fittings? You also avoid any potential environmental issues from the grease dissipating in the water around your boat.

If the tube that your shaft rides in can be made waterproof you should be able to simply convert to a conventional stuffing box and cutless bearing. If the grease input fitting is rusted then perhaps it can be cleaned out and plugged, making it waterproof.

If you are going through all of this work it may be worth replacing the "flexible hose" and the cutless bearing while you are there. You may also want to have your existing shaft checked by a prop shop for absolute true straightness. If there is any hint of a problem I'd replace the shaft too.

We replaced our shaft, cutless, flexible hose etc about 3 years ago. I learned a lot in the doing but will admit that I don't know everything there is to know on this subject.

Thanks to Cal31Windchaser for reviving your question. I'm a bit surprised nobody replied to it for 3 weeks.

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post #8 of 11 Old 12-30-2015 Thread Starter
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Re: Stern tube grease and propeller shaft

Hi everyone,

I've not been visiting the forum since almost one year, but I would like to give the community a follow up about the repair project, hoping it could help someone else. So, as planned, I refit the whole propeller gear last spring. New coupling, new stuffing box and a new cutlass bearing. Following the good advices on this post, I choose a stuffing box without greasing pin. For environnemental considerations, I've done my best to clean as much grease as possible from the tube before reinstalling the shaft. As a result, and after a little bit more than 100 hours of motor use, everything seems to be perfect. I've noticed nothing that could indicates problem of any kind during the sailing season. So thanks everyone for your help !
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Re: Stern tube grease and propeller shaft

Thanks for the follow up post Julien. It is too often that threads like yours get no follow up by the original poster.

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post #10 of 11 Old 12-30-2015
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Re: Stern tube grease and propeller shaft

Julien, sounds like you did a great job on the fix. Don't stay away so long. Would like to hear what else you are working on.
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