Manecraft deep Sea seal leak

[wizzer]

Well done for making it to your destination
Rather than criticise the Manecraft seal, I would have thought that it should be commended for only leaking 40 litres in 12 hours (3.3 litres per hour) with something so obviously wrong, as demonstrated by your video of the shaft movement.
Looks like there could be a cutlass bearing in the stern tube which is shot. I have seen situations where the stern tube cutlass bearing has popped out of the tube.
All of our advice & analysis of the situation is obviously based solely on what we can see from your posts, so, as before; good luck and we'll be interested to know the final outcome

 

[pcatterall]

Definite that a lift out required so that you can assess/order parts and repair.
You need to identify a yard which will lift you out and let you stay in the yard for a reasonable day rate so you can sort the job out without being under time/cost pressure.
Find one where you can stay on board in the yard.
It looks like whatever the original problem you will be buying a new seal and ( I think) cutlass bearing.
Good luck!

 

[geem]

Phil: if you do go for a Radice or Volvo seal, research them early. Both are available to fit only a fairly small range of stern tube sizes (the Volvo being the worst in this respect), which might oblige you to source an adaptor. I believe both are made by Radice, so there's little to choose between them in terms of quality, but the ease of greasing and self-burping qualities of the Radice are well worth having.

Our Manecraft seal has a water supply from the exhaust cooling circuit that self bleeds the seal. There is no greasing to do either. If you have longitudinal control over your prop shaft such as a thrust block and the prop runs true then the Manecraft seal works very well. If you cant achieve this longitudinal shaft control then I would use a different stern seal.

 

[macd]

Geem: my remarks about Radice/Volvo seals were purely in response to suggestions by others that the OP might fit one of them. If he does, he might find something helpful in there. It was not a comment either way on the Manecraft, of which I know little.

 

[Tranona]

Your comment is not correct. These seals are used in commercial water pumps and dont leak. I know of several that run at very high speed continuously 24/7/365 for years without a drip. The difference is that in these installations the alignment is perfect. If you install this kind of seal on a shaft that is bent or has longitudinal movement then you will have a leak. It is not a problem of the seal but the installation. We have an appropriate installation on our boat that has no longitudinal movement and we have never had the slightest drip. On a boat these seals will last many years if installed correctly.

You have made the point that they work if they are used as intended - on fixed shafts. The adaptation for marine use was poorly executed and could not cope with the shaft movement in modern boats with floating shafts. Plus it was very cheaply made to keep the price down. The original supplier dropped it very quickly because of the high failure rates and warranty claims. The product was then redesigned with the "safety" feature and is now I believe made in Australia.

There is nothing wrong in principle with face seals if they are properly engineered as is evidenced by the far superior design of PSS. However, they do still have drawbacks for use on leisure boats. First they require careful setting up of bellows pressure and they do not like being left idle in the water as the faces tend to stick together, sometimes so well that on putting into gear for the first time can split the bellows. Other times the deposits that build up can cause rapid wear.

In the 80s and 90s a number of firms tried to get into the market, mainly in the US with poor designs. I remember one in particular where the bellows was so poor that on one cruiser racer which surfed easily, water used to come up the stern tube and push the faces apart and let a jet of water in!

I was involved in that market during that period when all the new designs were coming in as alternatives to the stuffing box, so have a pretty good grasp of the issues involved. Great fan of the Volvo/Radice type seals, although they are not perfect for all installations so my preferred alternative would be Tides Marine seals.

 

[geem]

You have made the point that they work if they are used as intended - on fixed shafts. The adaptation for marine use was poorly executed and could not cope with the shaft movement in modern boats with floating shafts. Plus it was very cheaply made to keep the price down. The original supplier dropped it very quickly because of the high failure rates and warranty claims. The product was then redesigned with the "safety" feature and is now I believe made in Australia.

There is nothing wrong in principle with face seals if they are properly engineered as is evidenced by the far superior design of PSS. However, they do still have drawbacks for use on leisure boats. First they require careful setting up of bellows pressure and they do not like being left idle in the water as the faces tend to stick together, sometimes so well that on putting into gear for the first time can split the bellows. Other times the deposits that build up can cause rapid wear.

In the 80s and 90s a number of firms tried to get into the market, mainly in the US with poor designs. I remember one in particular where the bellows was so poor that on one cruiser racer which surfed easily, water used to come up the stern tube and push the faces apart and let a jet of water in!

I was involved in that market during that period when all the new designs were coming in as alternatives to the stuffing box, so have a pretty good grasp of the issues involved. Great fan of the Volvo/Radice type seals, although they are not perfect for all installations so my preferred alternative would be Tides Marine seals.

With the Manecraft seal we have installed it has a clean water supply from the exhaust cooling water so you dont get deposits on the surfaces. The Tides seal is excellent but is longer than the Manecraft seal so may not be a straight replacement for the Manecraft seal where space is tight. Slagging off a product that was similar to to a poor products in the 80s is hardly useful if the current product works well on the right installation today.

 

[Tranona]

With the Manecraft seal we have installed it has a clean water supply from the exhaust cooling water so you dont get deposits on the surfaces. The Tides seal is excellent but is longer than the Manecraft seal so may not be a straight replacement for the Manecraft seal where space is tight. Slagging off a product that was similar to to a poor products in the 80s is hardly useful if the current product works well on the right installation today.

But the fundamentals have not changed and there are far better products on the market, both face seals and lip seals.

Comparing your installation with the typical small yacht as shown in the OPs photo is not helpful. If space is a problem (and it is not for the OP) then a Radice seal at 110mm long is probably the shortest.

It is better to focus on the original question than wander off into situations that are very different. The OP (like the vast majority of boat owners) does not have an installation like yours. So, as I say not helpful.

 

[Topcat47]

I used Deep Sea Seals for the first fifteen years I owned Snark. I even (tho' this is not recommended ) polished the mating faces when they got badly scored. Sometimes they weeped a little but only when my shaft was bent did they leak badly. My last one was replaced when I had the shaft trued and replaced the mountings on my Engine about three years ago. I had a major failure shortly after that, entirely caused by the free end of a jubilee clip collecting the throttle cable which was hanging down too close to it. My fault entirely or not fixing the control cable out of the way. I replaced it with a PSS which has not been an unqualified success due to the relative hardness of the rubber bellows. Feeding a dribble of salt water from the primary cooling loop into the "bleed tube" is very effective though especially if you sit in a mud berth.

 

[Tranona]

The stiffness of the bellows is necessary to overcome the basic problem with face seals which is keeping the faces together at a more or less constant pressure and still allowing water to lubricate the faces. Given that fore and aft movement can be as much as +/- 6mm that is a big ask, and the weakness of the deep Sea seals. As geem says, if there is no movement in the shaft other than rotational and the seal is water fed, they work very well. However those conditions do not exist in small yachts with bouncy little engines and floating shafts. It is for those reasons that I would not fit a face seal when there are simpler, more secure and cheaper alternatives.

 

[Ruffles]

My deep sea seal leaked because the resonant frequency of the shaft coincided with the vibration of the engine at idle. The original stuffing box acted as a support for the shaft. Unforseen consequences etc.

The replacement Volvo seal contains an internal cutless bearing so reducing the lateral vibration.

But I think you have more than wobble!

 

[Topcat47]

As the owner of a bouncy little engine in a small yacht, I'm to saying you don't have a point. Access to my stern tube is problematic though and getting worse as I age so a fit and forget seal is better for me. I just have problems squeezing up the PSS by the recommended amount.

 

[Kurrawong_Kid]

Slight thread drift! I have a Halyard seal which I am told is no longer made. Are any of the above copies or modifications of the Halyard? Querying substitute spares.

 

[Topcat47]

You might get a better response by posting this as a new post.

 

[vyv_cox]

Slight thread drift! I have a Halyard seal which I am told is no longer made. Are any of the above copies or modifications of the Halyard? Querying substitute spares.

Halyard seals can be rebuilt quite easily using standard seals. The bushes may be a problem but they are simple and would not cost a lot to re-make. I have photos from a contributor ready to go on the website but technical problems have prevented me from posting them. E-mail me via the website and I can send them to you.

 

[Kurrawong_Kid]

Halyard seals can be rebuilt quite easily using standard seals. The bushes may be a problem but they are simple and would not cost a lot to re-make. I have photos from a contributor ready to go on the website but technical problems have prevented me from posting them. E-mail me via the website and I can send them to you.

Many thanks will do.

 

[phil28]

Hello everyone!!

So an update!

We ended up having the boat lifted And was on the hard for a week in the end. The cutlass bearing was completely worn, shaft was very very slightly out of alignment and rope cutter was completely destroyed.

We had the shaft taken out and straightened (luckily it wasn't too bad so did not require a new one.)

The cutlass bearing was replaced, a new rope cutter was fitted. Prop was cleaned and antifouled.

We changed the seal to a Volvo seal which seems to be a lot better IMHO.

Engine was aligned on the hard and then once we launched and we're back on our mooring the engine mounts were replaced as they were starting to sag quite badly.

After a very long day of realigning the engine, everything runs smooth and no leaks!!!

Thank you everyone for the help with the issue!