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Oceanis 37: leaking Volvo Stern Gland shaft seal when engine is running

Dec 14, 2016
39
Beneteau 37 Chichester
I have the standard Volvo Penta Stern Gland seal on my Beneteau Oceanis 37, with a 25mm shaft and 43mm stern tube. The boat is a 2009 model, and the Yanmar 3YM30 engine has around 800 hours.
The original seal did not leak, but was getting rather old, so I replaced it two years ago. After replacing it we had a slight leak, but only when the engine was running.
Despite being extremely careful with the lip seals during the process the only thing I could think was I had damaged them during the process, so this year I replaced it again (being very careful with the lip seals, following the manual etc.). There was no evidence of wear (that I could see) on the prop shaft where the seal sits.
After the second replacement we still have a slight leak only when the engine in running...see the video...
We were careful with all the "standard" stuff: greasing, burping etc.
Has anyone had experiences with:
  1. Out of balance prop shaft, prop or coupling causing this sort of problem
  2. Wear on the prop shaft
  3. Excessive engine vibration
  4. Prop shaft not being centred in the stern tube
Any ideas would be much appreciated please.
 

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Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
Rob,
Out of balance prop shaft, prop, coupling would all cause excessive shaft vibration; same as excessive engine vibration from broken engine mount, etc. In your video, there doesn't appear to be excessive vibration...about the same as mine. The only things that I can conclude are possibly excessive shaft wear at the shaft / seal interface or possibly minor misalignment of the engine or coupling. You can check the engine and coupling alignment and adjust accordingly in water and check the shaft for wear on your next haul out. I know that this is very frustrating after the efforts that you have made to keep up good preventive maintenance. One positive note is that is doesn't leak while stationary. The older designed bronze shaft seals /"stuffing boxes" with flax are actually designed to leak while operational; however, it is nice to have a seal that doesn't leak at all. My Volvo shaft seal is overdue for replacement; already purchased a new seal and plan to replace it on next haul out. You have me concerned now, because my present seal doesn't leak!
 
Mar 20, 2016
492
Beneteau 351 WYC Whitby
When i did mine there was wear on the prop shaft where seal sat so I added an R&D coupling moving it back 1.2 inches and allowing a bigger anode on shaft. I also machined a 25 mm delrin plug that went into tube centering the shaft . The engine was then aligned to shaft and it was out like 1/8 inch. Removed plug installed seal that was 3 years ago and not one drop
You did use the orange plastic piece to install the seal to protect the lips, I also grease mine using a straw flatening it out to slip into seal , and volvo grease only others may harden or destroy seal
 

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  • Like
Likes: BigEasy
Dec 14, 2016
39
Beneteau 37 Chichester
Thanks @BigEasy and @Mechone ,
We have wondered about balancing issues. I put a dial gauge on the prop shaft and it shows about 0.15mm of deviation, which is within tolerance according to the manufacturer. I don't know how dynamically balanced the prop is, and that may be one of the next areas for investigation.
Alignment is also something that I wondered about. I was also think about machining a plug to fit the stern tube and check the alignment, do you know the internal diameter of the stern tube please. I could then machine it up before I get the boat lifted.
We did use the lip protector (we keep it on the hose of the expansion tank, so we don't lose it!). And the flattened straw is our preferred method of greasing with the Volvo grease as you can judge both the quantity and location of the grease.
Regards Rob
 

RitSim

.
Jan 29, 2018
237
Beneteau 411 Branford
My seal began leaking last season about a gallon an hour. I ended up adding a second bilge pump as a temp fix. After close inspection, I noticed that 1) the shaft was not in the center of the shaft log and 2) the shaft log was leaking also. Fast forward to this year - changed the cutlass bearing, new shaft (for other reasons) and new seal. When doing the install, I resealed the shaft log and was installing the seal and coupling. I noticed that one of the engine mount nuts on the underside of the mount had travelled down about 1/2". When I brought the nut back to its proper position and aligned the engine, the shaft moved back to the center of the shaft log. No seal leak.

So check the engine mounts and alignment as part of your list.
 
Mar 20, 2016
492
Beneteau 351 WYC Whitby
Thanks @BigEasy and @Mechone ,
We have wondered about balancing issues. I put a dial gauge on the prop shaft and it shows about 0.15mm of deviation, which is within tolerance according to the manufacturer. I don't know how dynamically balanced the prop is, and that may be one of the next areas for investigation.
Alignment is also something that I wondered about. I was also think about machining a plug to fit the stern tube and check the alignment, do you know the internal diameter of the stern tube please. I could then machine it up before I get the boat lifted.
We did use the lip protector (we keep it on the hose of the expansion tank, so we don't lose it!). And the flattened straw is our preferred method of greasing with the Volvo grease as you can judge both the quantity and location of the grease.
Regards Rob
I have the plug in my nav desk will be going down tomorrow after work and will post measurement. .15mm is about .006 thousands runout ...too much no more than .003 TIR . I have done tons of coupling shafts and alignment as a Millwright for 40 years and .003 TIR is max and I shoot for no more than .001.I pulled my shaft dialed it .000 TIR installed the coupling and had to add another 2 setscrews in the coupling low side to get .001. I then machined across the facemaking it .000
If you look at my picture of R&D coulping you will see a red bolt this is to insert a feeler gauge at 12, 3,6 and 9 o'clock position to verify alignment of engine or adjust engine without coupling shaft unbolting
 
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Jan 10, 2018
220
Beneteau 331 Halifax
Mechone, with your skills I wish you would look at mine! I am in Nova Scotia. If you are down this way give me a call!!
 
May 17, 2004
3,421
Beneteau Oceanis 37 LE Havre de Grace
These Volvo shaft log non-seals are just stupid!!
Disagree with you on that. It’s a simple design that needs minimal maintenance and stays drip free in most cases. Not sure what’s causing the OP’s problem, but in the majority of Beneteaus that use this design they’re well regarded.
 
Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
These Volvo shaft log non-seals are just stupid!!
Nothing stupid about a seal that is simple, no mechanical parts to break, inexpensive, needs no adjustment, and is leak free. Only maintenance is lubricate it once or twice per year. I wouldn’t consider any other shaft seal; fourteen years of trouble free service.
 
Jul 13, 2009
36
Parker Skipjack 37 Clearwater
You say "leak free" - yet the person who sarted this thred and me have leaks!!! Wonder how many boats have sunk using this POS???
 
Jul 13, 2009
36
Parker Skipjack 37 Clearwater
Mine has probably the same hours as the engine----3200hours--Im pretty sure the very lazy 2 prior owners (both lawyers) never changed it--Volvo says to change it every 500 hours!! What fun!! So mine should have been changed 6 times!!!! POS POS. I have an idea to try as I cant get to a boatyard for awhile. Idea is to put a hose clamp over the seal area and tighten it ever so lightly to stop leak -of course I will lube it first-------must have been tried before??
 
Jan 7, 2011
2,823
Oday 322 East Chicago, IN
Mine has probably the same hours as the engine----3200hours--Im pretty sure the very lazy 2 prior owners (both lawyers) never changed it--Volvo says to change it every 500 hours!! What fun!! So mine should have been changed 6 times!!!! POS POS. I have an idea to try as I cant get to a boatyard for awhile. Idea is to put a hose clamp over the seal area and tighten it ever so lightly to stop leak -of course I will lube it first-------must have been tried before??
You are complaining about a seal that leaks, but that should have been changed 6 times by now? Wow.

I think the hose clamp will deform the seal, and make the leak worse.…but let us know how it goes.

Greg
 
Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
I have an idea to try as I cant get to a boatyard for awhile. Idea is to put a hose clamp over the seal area and tighten it ever so lightly to stop leak -of course I will lube it first-------must have been tried before??
Never heard of anyone trying that, but it sounds like a good idea! Let us know if it works for you. As I previously stated, mine is leak free; however, if it starts leaking, the hose clamp idea would be worth trying. I actually purchased another Volvo seal as I was planning to haul out and replace it this fall; however, that is going to be delayed at least until Spring.
 
Mar 20, 2016
492
Beneteau 351 WYC Whitby
Never heard of anyone trying that, but it sounds like a good idea! Let us know if it works for you. As I previously stated, mine is leak free; however, if it starts leaking, the hose clamp idea would be worth trying. I actually purchased another Volvo seal as I was planning to haul out and replace it this fall; however, that is going to be delayed at least until Spring.
My buddy sailed with a hose clamp around it for 2 years not knowing he was to lubricate it with" Volvo grease only" ,he never lubed it. Changed it out 3 years ago lube it burp it no leaks and same as mine
 
Nov 21, 2007
474
Beneteau Oceanis 34 Kingston, WA
Is it possible to put too much grease in it?

I had mine replaced last fall. I had noticed uneven wear as well as noticing water coming in when we were motoring, and I became paranoid about it. At one point, I used a zip tie to add a little pressure to help it keep a seal. I thought a hose clamp would add too much pressure and increase friction and wear. Ultimately I had it replaced ($$), and things stayed dry for a while, now I'm getting water in while motoring again. :banghead: I have thought that I had the source of the water identified at one time or another, and have blamed it on just about every possible component of the cooling water intake, the exhaust, and the shaft seal... only to have the leak return shortly after I think that I've fixed it. My most recent recurrence of water coming in just started recently. I'm going to add some grease, and I was wondering if it's possible to over do it?
 
May 17, 2004
3,421
Beneteau Oceanis 37 LE Havre de Grace
I have read that too much grease can block water flow through the cutlass. I don’t know if that’s real or myth, or how much is too much, it I guess it’s a consideration.

If you’re not sure you’ve pinned down the source of the water yet you could consider the seal between the shaft log and the skeg. In some Beneteaus that seal fails letting some water into the area around the shaft seal.
 
Nov 21, 2007
474
Beneteau Oceanis 34 Kingston, WA
I have read that too much grease can block water flow through the cutlass. I don’t know if that’s real or myth, or how much is too much, it I guess it’s a consideration.

If you’re not sure you’ve pinned down the source of the water yet you could consider the seal between the shaft log and the skeg. In some Beneteaus that seal fails letting some water into the area around the shaft seal.
At least I'd have stopped water from getting somewhere! ¯\_(ツ)_/¯ I think all of the possible sources of water are tag-teaming me, when I fix one, something else starts. The only consistent symptom is that it's visible around the engine tray, makes its way forward, and then gets occasionally pumped out by the bilge pump. Sometimes there is water in the low spot under the prop shaft (there is now), sometimes not... you know the size of the bilge in these boats, it only pumps out about 16 - 24 ounces at most, and it doesn't activate the pump very often.