Bukh gear box seals

[alan54]

I have a small oil leak from my DV20 Bukh gear box rear seals. Has anyone else had this problem ? How easy would it be for a competant DIY to replace them ? Can this be done while the boat is afloat ?
Grateful for any help !
regards
alan

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[Rick]

Yes and no - it's straight forward, about the same as doing a rear gearbox seal on a car, with one mod - on a car you get to drop the prop shaft - here you need the move the engine / g'sack forward first.

The actual seal swap is minor compared to the logistics of gaining access. Your engine weighs over 200kg's, so it isn't simple - if you can organise to move it forward say 300 mm and have access to the back to work, you're right - if not (IMHO), then just pay someone who does these things for a living.

Remember to allow for lining up after you poke the engine back.

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[jerryat]

Hi Alan,

I don't know what boat you have, but in my Fulmar I was able to change the seal (there's only one at the rear - output shaft) while afloat in the Med. though I had a good 300mm between the gear take-off flange and the stern tube.

If you have to move the engine, it's harder and much more complicated work, but the actual bearing change is, of course, the same.

Undo the flange bolts and GENTLY slide the shaft aft as far as necessary, ensuring that you don't let it slide right out!! I cannot remember whether I had to remove the gearbox oil, but don't think so.

You then do the following:-

1. Unscrew the nut off the output shaft.
2. Pull off the output shaft flange - you may well need a puller here, though in my case it slid off the splines after a gentle tap with a hammer. Try gentle levering if the 'tap' fails, but don't overdo it. Use a puller if in any doubt.
3. The output shaft oil seal is now visible and can be prised out.
4. Smear the new seals lip with a little grease and a thin layer of permanent jointing paste on the rim and drive home with a suitable drift. Incidentally the seals can be bought from most bearing stockists but take the old one for reference. Size is 32mm int'l diam x 45mm o/a external diam. x 7mm wide )
5. Re-assemble remainder in reverse order.

Note!!! Fit the new seal so that it seats tightly against the tapered roller bearing inner collar, a distance of 22.5 +/- 0.5mm measured from the end of the output shaft to the face, i.e. visible, part of the seal. Make sure the flange hub is clean and lightly greased before pushing it into the new seal.

I do not have torgue settings for the shaft nut but did mine up as tight as I could using a short ratchet and socket. It's been fine for the last seven years!

As you can see, none of the above is rocket science (one of the delights of Bukh engines) so do have a go yourself. If you have any problems I'll be happy to help. Just PM me and I'll give you my 'phone number for a chat.

Hope this helps.

Good sailing!





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[bigshineybike]

Torque setting is 100Nm.