Bukh final drive seals

[mcalan]

I own a Bukh 36 Saildrive on a 35 foor cruising yatcht, which was out of the water when purchased last year. I decided to do as much maintainance as was possible before returning to the water.
This maintainace included changing the saildrive gaiters and also the oil in the gearbox and saildrive leg.On completion the boat was put back in the water in September last year.

Each time I visited the boat I started the engine for about 30 minutes and occasionaly put in in both forward and reverse gears to keep the linkages free etc.
Last week on a shakedown trip I noticed emulsified oil in the engine bilge. On investigation it was coming from the breather on top of the gearbox and when I removed the dip stick it began coming out at an alarming rate.

I immeadiatly had the boat lifted and formed the idea it was either the oil drain plug had dropped out or the final drive shaft seal had failed.

The oil drain plug was present and tight so I then removed the propeller and anode assembly and noticed that the outer seal appeared to be in the wrong way around (by this I mean I could see the flat face of the seal with the number on.)
I ordered some new seals from Bukh UK and the very helpful man also sent me an exploded diagram of the drive leg.
I am now in the process of reassembling the final drive complete with 2 new seals and O rings but am unsure which way the seals actualy go I spoke to Bukh and they stated they didnt know as this had never come up before.
I have put them in with the inner seals face towards the rear of the boat and the rear most seal face to wards the front of the boat i.e opposite or face to face.

Has anyone had an experience of repacing these seals that may be able to shed some light on this?
I have spoken to a local VP dealer as its a similar set up on a VP saildrive and he agreed that they were in fact in wrong and I am correct but I would really appreciate a second opinion on this

Alan Mac

 

[RichardS]

I own a Bukh 36 Saildrive on a 35 foor cruising yatcht, which was out of the water when purchased last year. I decided to do as much maintainance as was possible before returning to the water.
This maintainace included changing the saildrive gaiters and also the oil in the gearbox and saildrive leg.On completion the boat was put back in the water in September last year.

Each time I visited the boat I started the engine for about 30 minutes and occasionaly put in in both forward and reverse gears to keep the linkages free etc.
Last week on a shakedown trip I noticed emulsified oil in the engine bilge. On investigation it was coming from the breather on top of the gearbox and when I removed the dip stick it began coming out at an fair old rate.

I immeadiatly had the boat lifted and formed the idea it was either the oil drain plug had dropped out or the final drive shaft seal had failed.

The oil drain plug was present and tight so I then removed the propellor and anode assembly and noticed that the outer seal appeared to be in the wrong way around (by this I mean I could see the flat face of the seal with the number on.)
I ordered some new seals from Bukh UK and the very helpful man also sent me an exploded diagram of the drive leg.
I am now in the process of reassembling the final drive complete with 2 new seals and O rings but am unsure which way the seals actualy go I spoke to Bukh and they stated they didnt know as this had never come up before.
I have put them in with the inner seals face towards the rear of the boat and the rear most seal face to wards the front of the boat i.e opposite or face to face.

Has anyone had an experience of repacing these seals that may be able to shed some light on this?
I have spoken to a local VP dealer as its a similar set up on a VP saildrive and he agreed that they were in fact in wrong and I am correct but I would really appreciate a second opinion on this

Alan Mac

As a general rule, I believe that the flexible part of the seal (sometimes with a coil spring round it) has to face towards the liquid which you want to prevent from going past the seal, whether that be oil or water.

Richard

 

[mcalan]

Thanks that would agree with the way I have installed them ie the front inner one keeps oil in and the outer one keeps water out

I was worried about the steel spring being exposed to sea water but as its stainless do I need to be concerned?

 

[KenMcCulloch]

Thanks that would agree with the way I have installed them ie the front inner one keeps oil in and the outer in keeps water out

I was worried about the steel spring being exposed to sea water but as its stainless do I need to be concerned?

Seals with stainless steel springs in seawater pumps seem to do OK so no reason why yours should not also do fine.

 

[vyv_cox]

Seals with stainless steel springs in seawater pumps seem to do OK so no reason why yours should not also do fine.

Not saildrive seals but water pump ones. My Yanmar water pump seals failed a couple of years ago. When I went to the local suppler I was advised to fit the Volvo ones, which have stainless springs, whereas the Yanmar seals have a copper based metal that corrodes quite quickly. The stainless ones are so far doing well.

I agree that the standard fitting method is with the spring facing the liquid. where there are two liquids, just as with a water pump, the same applies, so face to face in your case would seem to be correct.

 

[actionoptics]

water in the gear box

When the seals failed for a second time in 12 months on my Bukh 24 I found that someone (no names but it was a professional marine engineer) had "cured" the original leak by simply fitting a third seal. The actual cause of the seals failing was a worn sleeve onto which the seals press. A new sleeve was fitted together with two new seals and I have not had any problems for 6 years and over 800 hours motoring.

 

[david_bagshaw]

No bukh experience but on Yamaha outboards I have had, the shaft seals face each other, so one inside springs to gear oil, other springs to the water.

 

[Malish]

Not saildrive seals but water pump ones. My Yanmar water pump seals failed a couple of years ago. When I went to the local suppler I was advised to fit the Volvo ones, which have stainless springs, whereas the Yanmar seals have a copper based metal that corrodes quite quickly. The stainless ones are so far doing well.

Probably no need to buy branded seals unless it is convenient. The seals should have a generic ID code on the flat face to give sizing and there are numerous e-suppliers who can supply them with stainless steel springs. I have used these chaps in the past:

http://simplybearings.co.uk/shop/

 

[mcalan]

Update It gets Worse!!!

On returning to the boat today with the intention of re installing the final drive shaft complete with new O rings and seals I noticed oily wter leaking down the outside of the sail drive leg.
This would appear to be from the original emusified oil/water in the bilge. On closer examination there was also water dripping from the six bolts which connect the gearbox to the saildrive.
These bolts also appeared to be loose,I now suspect that the problem was not the final drive shaft seals as originaly suspected but may be from the mating faces of the gearbox and saildrive.
I now intend to undo the large circular alluminium ring around the saildrive gaiters and check for water ingress.
If there is non present I will re torque the bolts up and am considering removing them and drilling a hole in the bolt heads to facilitate the installation of a saftey lacing wire.
I will also used some loctite 243 on the bolts themselves.
But Im rather worried that there is no gasket between the mating faces of the gearbox and saildrive should I pehaps use a liquid gasket compound?

Thnanks

Alan Mac

 

[Tranona]

Think you need to investigate further. If oil and water are coming down the outside of the saildrive, this suggests a failure of either the diaphragm or the fastenings. Nothing should leak out here if it is sound. You also need to check about whether there should be a gasket from the engine to the gearbox. Would not affect "leaks" as there should be no liquid in there unless the crankshaft or gearbox input shaft seals have failed. On Volvos there is an isolating membrane to insulate the two components electrically.