I am taking the opportunity of a long weekend and cool weather to take the Bukh diesel engine out of my Cavalier 28. The boat is in a berth and is not out of the water, on a slip. The engine is connected to a 1" shaft with a flange. This is the first time I have attempted anything like this.

I have worked carefully around the engine to photograph, disconnect, label and note the control cables, water lines, fuel lines, electric cables exhaust pipes, and have got to the aft end of the engine and the coupling between the gear box and shaft.

I have removed the bolts from the coupling and shaft, and confirmed that they are not locked together by prising apart the coupling flanges by a few millimetres. Prising apart the flanges pushes the shaft drive aft-wards away from the gear box, but I noticed that the water pressure on the other side of the seal pushes the shaft back again, forwards towards the gear box. Obviously, the gear box stops the shaft from moving any further forward.

I thought I had better pause here, before I break a seal or something and fill the boat with water. So, I left the engine and gear box in place, to ask the advice of the brains trust here. I'm also waiting on a return call from the person who fitted my prop and shaft about 2 years' ago.

The boat has a P bracket just forward of the propellor. I assume that, if the shaft were allowed to travel forward, the prop will rest on the P bracket, preventing further, forward movement. However, I don't know how far forward the shaft can travel before it breaks a seal. Presumably, there is a small gap between the prop and P bracket, and the seal can tolerate the movement without becoming un-sealed, but I would like to check.

Any thoughts or advice?

The photo below shows the coupling after the removal of the 4 flange bolts and 4 bolts on the "sleeve". The red thing is the gear box.

I've not removed an engine before, but an engineer did it.
The shaft will move forwards and backwards by about an inch, maximum maybe 2. It will be stopped by the prop coming in, and in the other direction the flange will stop it falling out backwards, or a rudder blade. So that flange needs to stay on.
I'd suggest getting a texta and drawing some lines to show where the 2 halves of the flange meet, so that (in the absence of shims) you have a starting point where they met and align.
You'll also need to turn off the valve for raw cooling water to the engine.

I pulled out the old engine from my boat and put in the new all while tied to a marina berth. Have done the same thing on the hard and I actually reckon doing it in the berth was easier. My boat went for about 5 months without the engine and just the shaft hanging free as I waited for the new engine to arrive at the height of covid, no problem at all because the flange will stop it sliding past the seal and there isn't really anything likely pull the shaft from the boat.

One tip I will give is to go to Bunnings and buy the small lever block and a couple of small slings. I used these to manipulate the engine out of the engine bay and companion way hatch (in my case) as I lifted it out with a chain block attached to the main halyard and boom. The lever block also made pulling the new engine into position really easy. My engine had to be slid into position, so I also purchased a couple of cheap soccer balls to use as tyres to assist in sliding it onto the engine beds. One more thing, measure the dimensions of the engine to make sure it will actually pass through any hatches. You may need to unbolt stuff to reduce the size.

Good luck!

Hi,
just wondered why you are removing the Bukh?
Are you reconditioning it or replacing it, if so what with?
interested as I have the same engine.
cheers

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Cockpit said..
Hi,
just wondered why you are removing the Bukh?
Are you reconditioning it or replacing it, if so what with?
interested as I have the same engine.
cheers

Same here.

Achenar,
sounds like your under control.

I have no experience with your type of seal, however if you move the boat after the prop shaft will spin, I'd secure it, you never know what could happen, perhaps not a problem for you.

I'd also split the gearbox/engine and have a look at the rubber star drive, pulsation dampener thing'o, between the box and engine. mine was heat effected and cracked, after replacing there was a slight reduction in vibration but that could have been alignment too. Also replace the rear gearbox oil seal, try and get nitrile or high temp seal if you can, I'm not sure what model Bukh you have but Bukh gearboxes tend to run warm to hot, both are easy to replace and could save you removing the engine latter. I tried to find the dampener on line, no luck, and ended up going to Bukh at Taren Point.

Keep note of any shims under the engine mounts, put them back in the same spot when reinstalling and your "X" axis should be OK. When I lined up the engine I had a couple of wedges cut from some 4 x 2, when the engine was about where I wanted it I placed the wedges between side of the engine and engine beds and when I needed to move the engine a mill or so I gave the to of the wedge a LIGHT tap with a hammer, worked like a charm, saved a lot of mucking about and got the "Y" axis spot on. I always get X & Y's wrong but I'm sure you know what I mean.

Good luck Mike

I would suggest a small piece of rubber hose split so it fits over that bare SS shaft and secure it with a hose clamp. This will keep the shaft from sliding back. It's best to keep the shaft near it's worn part in the bearings. There may be a small lip on that flange of about 2 or 3 mm so allow for that much shaft movement.
Are you sure that what ever needs to be done can't be done in place?
There might be some shell on the shaft in front of the P bracket stopping the shaft going back too.

If you leave the PSS as is , just make sure you arrange a fixture that keeps the shaft rotor preloaded against the seal face that is attached to the rubber bellow. The seal mechanism needs to be kept in compression .
The shaft can be moved aft by loosening the collar on the shaft and sliding the shaft though it.

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julesmoto said..

Cockpit said..
Hi,
just wondered why you are removing the Bukh?
Are you reconditioning it or replacing it, if so what with?
interested as I have the same engine.
cheers

Same here.

The problem with the Bukh is that there is not much wrong with it. it has slow oil and diesel leaks (that fill the boat with a foul smell), the electrics are a mess, it is 40 years old, the bearings are stuffed. However, it starts, runs and stops nicely, pushes the boat along at 5 to 5.5 knots on flat water, does not spew out black stuff, and fits the engine beds and all the other fittings. A new engine will cost about $15K ($9K - $10K engine, plus fittings, labour etc.), which may be 1/2 the value of the boat (in the current market).

I have previously posted my attempts to fix it in-situ in other threads.

After much prevaricating and considering an engine replacement, I have decided on the following strategy

1 Remove engine - I would have to do this in any case
2 Take the engine to a shop to get it reconditioned
3 If the shop says the engine is dead, get a new engine. Be happy that I tried the cheaper option.
4 If the shop says the engine is serviceable, recondition (maybe $2K, maybe more) and re-fit old engine with new fittings, as required (maybe $3K, maybe more)

I am optimistic that the engine is serviceable. When pulling it apart, I found a dodgy fuel line, which could be the diesel leak (it might not be). I might also have found the general location of the oil leak. Also, it burns cleanly. We shall see. First, I need to get it out.

Phil and Mike - Thanks for the tips on marking the flange and measuring or recording or wedging bearing shims.

The cooling system is direct seawater. The intake stopcock is well and truly closed.

I don't think I can split the gearbox from the engine in-situ, but will take another look at it today.

I have removed an engine at anchor after having seen large Detroit diesels removed from an engine room, up 2 or 3 flights of stairs.
All done with chain blocks.

The secret is to remove EVERYTHING from the block.
Alternator and all brackets. Starter motor, head, foot mounting brackets if they protrude an of the course the big heavy gear box.
You want to get the lump as compact (no stuff sticking up) and light as you can.
Fitting all that stuff on the cabin floor might sound like a hassle, but if you have everything in buckets , cleaned and ready to bolt on it's not that big a job.
Then slide her back in and Bob's your uncle, as they say.

All the best

gary

I did this very job on a swing mooring. I took out the Bukh 10 hp and replaced it with a Beta 14 hp. I posted the process on this forum somewhere if you can find it. It's quite doable. I did it single handed.
Good luck. Sam.

Success!

Removed everything I could reach, undid the coach bolts under the bearings, slid the engine forward a couple of inches and ... no leaks. Yay! The shaft seal held and the boat did not sink. I'm getting some help tomorrow to lift the engine out of the boat.

Found some nightmares - one of the bearing brackets had sheared clean through. The forward port side of the engine was supported by the starter motor casing resting on the sticking-up-bearing-bolt. Also, the coach bolts were obviously what a PO had in the garage at the time, which left me with a lucky dip. For 8 bolts holding the bearings on the engine beds, there were 16mm, 11/16 and 17mm bolts (or, those were the socket sizes that fitted).

For the curious, its either a Bukh 10 or a Bukh 8 that outputs 10HP with a single cylinder and flywheel. The rear bearing brackets are 50mm higher than the forward bearing brackets and it has a bolt-on alternator with a belt running around the flywheel (or, it did before I removed it). If I could get the flywheel off, it would be much lighter, but the 33.5mm nut (?) is seized.

By the sound of things it looks like you've made the right call, finding broken engine mounts etc & will be heaps easier to sort the dodgy fuel lines and fix that oil leak. I imagine the flywheel nut would have a highish torque so would need a sharp wack on an extension bar to free it

Great job so far Ach but still a fair bit can be removed.
Are those mounting brackets narrower than the compaionway??

Check the thread on the end of the crank holding the flywheel on. It could be a lefthander.

It will probably need an impact driver or slogging spanner to get the nut off.

I think the Buhk people in Sydney do reconditioned exchange engines.

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Achernar said..


The problem with the Bukh is that there is not much wrong with it. it has slow oil and diesel leaks (that fill the boat with a foul smell), the electrics are a mess, it is 40 years old, the bearings are stuffed. However, it starts, runs and stops nicely, pushes the boat along at 5 to 5.5 knots on flat water, does not spew out black stuff, and fits the engine beds and all the other fittings.

I would be quitting right there. The engine starts and runs, pushes the boat along at 5 knots and does not blow smoke. For 10hp in a 28 footer that's pretty damn perfect. If the engine was rebuilt is would not go faster. If a 3 cylinder 20 hp Kubota was fitted it would not go faster really.
I would be moving the engine forward a bit and raising it up a bit to get better access and repairing the minor faults. Take the starter motor and alternator to an auto electrician for a half life refit. Make a whole new wiring loom with quality wire from Jaycar. Buy a 12v electric fuel pump off eBay just for priming. Replace all the diesel fuel pipes and hoses.
If you are not adding oil the engine is not burning any the bearings are probably OK for another 40 years.
When the engine is running next use FTC in the fuel for awhile and flush the engine block cooling passages with Metal Gleam or equivalent every 18 months or so.

I replaced mine on a mooring , sort of , got it ready to pullout then got towed to the local slipway where we used the dock crane to lift it out of the boat. Towed back to mooring where I did all the bits necessary for the new engine install. Mine was an old " green death" Volvo where you could buy all the parts for , except the ones that failed , lol. Now if it was a buhk I would have fixed it up. If your buhk is leaking from oil seals , speedsleeves ( I think they are called ) can be fitted over the shafts and oversized oils seals to suit . I'm with Romona , maybe a set of bearings if really bad . The problem with older engines is , they go forever with lots of noise. Still wish mine was a buhk, it would still be there. With the prop shaft I just made sure it couldn't move either direction with blocks of wood.

Hi Ach
You haver a PSS shaft gland which needs the pre load on the rubber bellows to maintain the seal between the ceramic (dark) disc and the stainless collar. The pre load on the rubber bellows is what is pushing the shaft forward. You are correct. The shaft will stop moving forward when the prop boss touches the P bracket. Mark the shaft with a permanent marker then loosen the grub screws in the ss collar and push the pre load back onto the bellows while the engine is out. When you re install the engine make sure you go back to the mark so you will know you have the correct clearance between the p bracket and prop boss. This is assuming the coupling position is going to be the same fore and aft when the engine is re installed.
If this is confusing give me a call.

0429922931

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samsturdy said..
I did this very job on a swing mooring. I took out the Bukh 10 hp and replaced it with a Beta 14 hp. I posted the process on this forum somewhere if you can find it. It's quite doable. I did it single handed.
Good luck. Sam.

Are you happy with the Beta Sam?

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troubadour said..
Hi Ach
You haver a PSS shaft gland which needs the pre load on the rubber bellows to maintain the seal between the ceramic (dark) disc and the stainless collar. The pre load on the rubber bellows is what is pushing the shaft forward. You are correct. The shaft will stop moving forward when the prop boss touches the P bracket. Mark the shaft with a permanent marker then loosen the grub screws in the ss collar and push the pre load back onto the bellows while the engine is out. When you re install the engine make sure you go back to the mark so you will know you have the correct clearance between the p bracket and prop boss. This is assuming the coupling position is going to be the same fore and aft when the engine is re installed.
If this is confusing give me a call.

0429922931

OK, thanks. I think I know what you mean.

We successfully lifted the engine out.

TIP 1 - Make a cradle. I knocked up a cradle from some spare timber and got it under the engine before moving it. It makes handling much easier, but it also means you can put it down without doing damage - e.g. on the companionway sill, cockpit seats, combing and toe rail.

TIP 2 - Strip off as much as you can. I took off the mounting brackets, and half the water pump. A hex screw in the other half of the water pump refused to yield, so I could not reduce weight and protrusions any further.

TIP 3 - Get some mates. Three of us made light work of it

TIP 4 - Clean up diesel with diesel. Simply dampen a rag of paper towel with clean diesel fuel and use it to wipe the engine-black and oil stains off surfaces. Its good for an initial clean, and you can follow up with a nicer-smelling clean, later. The photo shows some of the black mess in the engine bay, but it came off nicely with a rag dampened with diesel fuel.

For the curious, the blue tape marks the bearing positions, but I doubt I will be putting the old bearings back. Even if I use the old bearings, the beds have some interesting cracks and other "undocumented" features, so I might get to work on them, too. In any case, I'll wait to hear the diagnosis from the engine reconditioning.

Looking good. The electric motor is going to look very small in that space.

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troubadour said..

samsturdy said..
I did this very job on a swing mooring. I took out the Bukh 10 hp and replaced it with a Beta 14 hp. I posted the process on this forum somewhere if you can find it. It's quite doable. I did it single handed.
Good luck. Sam.

Are you happy with the Beta Sam?

Yes, very happy. The Bukh was extremely tired and the compression was so low it would hardly start. I considered an overhaul but the person I trusted to do it went out of business and I was not interested in a Taren Point one.

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Achernar said..
Success!

Removed everything I could reach, undid the coach bolts under the bearings, slid the engine forward a couple of inches and ... no leaks. Yay! The shaft seal held and the boat did not sink. I'm getting some help tomorrow to lift the engine out of the boat.

Found some nightmares - one of the bearing brackets had sheared clean through. The forward port side of the engine was supported by the starter motor casing resting on the sticking-up-bearing-bolt. Also, the coach bolts were obviously what a PO had in the garage at the time, which left me with a lucky dip. For 8 bolts holding the bearings on the engine beds, there were 16mm, 11/16 and 17mm bolts (or, those were the socket sizes that fitted).

For the curious, its either a Bukh 10 or a Bukh 8 that outputs 10HP with a single cylinder and flywheel. The rear bearing brackets are 50mm higher than the forward bearing brackets and it has a bolt-on alternator with a belt running around the flywheel (or, it did before I removed it). If I could get the flywheel off, it would be much lighter, but the 33.5mm nut (?) is seized.

My Bukh 10HP is definitely different than yours so I'm guessing yours is the 8hp version. mines from my 1985 Cav 28.